diff --git a/nw/__init__.py b/nw/__init__.py
index 937a675b..f6458ae9 100644
--- a/nw/__init__.py
+++ b/nw/__init__.py
@@ -209,9 +209,7 @@ def main(sysArgs=None):
     pkgLogger.addHandler(cHandle)
     pkgLogger.setLevel(logLevel)
 
-    logger.info("Starting novelWriter %s (%s) %s" % (
-        __version__, __hexversion__, __date__
-    ))
+    logger.info("Starting novelWriter %s (%s) %s", __version__, __hexversion__, __date__)
 
     # Check Packages and Versions
     errorData = []
diff --git a/nw/config.py b/nw/config.py
index 06fe540e..b076860f 100644
--- a/nw/config.py
+++ b/nw/config.py
@@ -272,7 +272,7 @@ class Config:
             confRoot = QStandardPaths.writableLocation(QStandardPaths.ConfigLocation)
             self.confPath = os.path.join(os.path.abspath(confRoot), self.appHandle)
         else:
-            logger.info("Setting config from alternative path: %s" % confPath)
+            logger.info("Setting config from alternative path: %s", confPath)
             self.confPath = confPath
 
         if dataPath is None:
@@ -282,11 +282,11 @@ class Config:
                 dataRoot = QStandardPaths.writableLocation(QStandardPaths.DataLocation)
             self.dataPath = os.path.join(os.path.abspath(dataRoot), self.appHandle)
         else:
-            logger.info("Setting data path from alternative path: %s" % dataPath)
+            logger.info("Setting data path from alternative path: %s", dataPath)
             self.dataPath = dataPath
 
-        logger.verbose("Config path: %s" % self.confPath)
-        logger.verbose("Data path: %s" % self.dataPath)
+        logger.verbose("Config path: %s", self.confPath)
+        logger.verbose("Data path: %s", self.dataPath)
 
         self.confFile = self.appHandle+".conf"
         self.lastPath = os.path.expanduser("~")
@@ -310,8 +310,8 @@ class Config:
         # Internationalisation
         self.nwLangPath = os.path.join(self.assetPath, "i18n")
 
-        logger.verbose("App path: %s" % self.appPath)
-        logger.verbose("Last path: %s" % self.lastPath)
+        logger.verbose("App path: %s", self.appPath)
+        logger.verbose("Last path: %s", self.lastPath)
 
         # If config folder does not exist, create it.
         # This assumes that the os config folder itself exists.
@@ -319,7 +319,7 @@ class Config:
             try:
                 os.mkdir(self.confPath)
             except Exception as e:
-                logger.error("Could not create folder: %s" % self.confPath)
+                logger.error("Could not create folder: %s", self.confPath)
                 logException()
                 self.hasError = True
                 self.errData.append("Could not create folder: %s" % self.confPath)
@@ -342,7 +342,7 @@ class Config:
                 try:
                     os.mkdir(self.dataPath)
                 except Exception as e:
-                    logger.error("Could not create folder: %s" % self.dataPath)
+                    logger.error("Could not create folder: %s", self.dataPath)
                     logException()
                     self.hasError = True
                     self.errData.append("Could not create folder: %s" % self.dataPath)
@@ -392,7 +392,7 @@ class Config:
                 lngFile = "%s_%s" % (lngBase, lngCode.replace("-", "_"))
                 if lngFile not in self.qtTrans:
                     if qTrans.load(lngFile, lngPath):
-                        logger.debug("Loaded: %s" % os.path.join(lngPath, lngFile))
+                        logger.debug("Loaded: %s", os.path.join(lngPath, lngFile))
                         nwApp.installTranslator(qTrans)
                         self.qtTrans[lngFile] = qTrans
 
@@ -898,10 +898,10 @@ class Config:
         """
         if thePath in self.recentProj:
             del self.recentProj[thePath]
-            logger.verbose("Removed recent: %s" % thePath)
+            logger.verbose("Removed recent: %s", thePath)
             self.saveRecentCache()
         else:
-            logger.error("Unknown recent: %s" % thePath)
+            logger.error("Unknown recent: %s", thePath)
             return False
         return True
 
diff --git a/nw/core/document.py b/nw/core/document.py
index 70519c2a..8093bb75 100644
--- a/nw/core/document.py
+++ b/nw/core/document.py
@@ -73,7 +73,7 @@ class NWDoc():
             return None
 
         docFile = self._docHandle+".nwd"
-        logger.debug("Opening document %s" % docFile)
+        logger.debug("Opening document: %s", docFile)
 
         docPath = os.path.join(self.theProject.projContent, docFile)
         self._fileLoc = docPath
@@ -120,7 +120,7 @@ class NWDoc():
         self.theProject.ensureFolderStructure()
 
         docFile = self._docHandle+".nwd"
-        logger.debug("Saving document %s" % docFile)
+        logger.debug("Saving document: %s", docFile)
 
         docPath = os.path.join(self.theProject.projContent, docFile)
         docTemp = os.path.join(self.theProject.projContent, docFile+"~")
@@ -170,7 +170,7 @@ class NWDoc():
             if os.path.isfile(chkFile):
                 try:
                     os.unlink(chkFile)
-                    logger.debug("Deleted: %s" % chkFile)
+                    logger.debug("Deleted: %s", chkFile)
                 except Exception as e:
                     self._docError = str(e)
                     return False
@@ -237,7 +237,7 @@ class NWDoc():
                     self._docMeta["layout"] = nwItemLayout[metaBits[1]]
 
         else:
-            logger.debug("Ignoring meta data: '%s'" % metaLine.strip())
+            logger.debug("Ignoring meta data: '%s'", metaLine.strip())
 
         return
 
diff --git a/nw/core/index.py b/nw/core/index.py
index 98272f7e..c7d7a432 100644
--- a/nw/core/index.py
+++ b/nw/core/index.py
@@ -85,7 +85,7 @@ class NWIndex():
     def deleteHandle(self, tHandle):
         """Delete all entries of a given document handle.
         """
-        logger.debug("Removing item %s from the index" % tHandle)
+        logger.debug("Removing item '%s' from the index", tHandle)
 
         delTags = []
         for tTag in self._tagIndex:
@@ -107,7 +107,7 @@ class NWIndex():
         moved from the archive or trash folders back into the active
         project.
         """
-        logger.debug("Re-indexing item %s" % tHandle)
+        logger.debug("Re-indexing item '%s'", tHandle)
 
         tItem = self.theProject.projTree[tHandle]
         if tItem is None:
@@ -217,7 +217,7 @@ class NWIndex():
             self.indexBroken = True
 
         tEnd = time()
-        logger.debug("Index check took %.3f ms" % ((tEnd - tStart)*1000))
+        logger.debug("Index check took %.3f ms", (tEnd - tStart)*1000)
         logger.debug("Index check complete")
 
         if self.indexBroken:
@@ -239,16 +239,16 @@ class NWIndex():
         theRoot = self.theProject.projTree.getRootItem(tHandle)
 
         if theItem is None:
-            logger.info("Not indexing unknown item %s" % tHandle)
+            logger.info("Not indexing unknown item '%s'", tHandle)
             return False
         if theItem.itemType != nwItemType.FILE:
-            logger.info("Not indexing non-file item %s" % tHandle)
+            logger.info("Not indexing non-file item '%s'", tHandle)
             return False
         if theItem.itemLayout == nwItemLayout.NO_LAYOUT:
-            logger.info("Not indexing no-layout item %s" % tHandle)
+            logger.info("Not indexing no-layout item '%s'", tHandle)
             return False
         if theItem.itemParent is None:
-            logger.info("Not indexing orphaned item %s" % tHandle)
+            logger.info("Not indexing orphaned item '%s'", tHandle)
             return False
 
         # Run word counter for the whole text
@@ -257,16 +257,16 @@ class NWIndex():
 
         # If the file is archived or trashed, we don't index the file itself
         if self.theProject.projTree.isTrashRoot(theItem.itemParent):
-            logger.info("Not indexing trash item %s" % tHandle)
+            logger.info("Not indexing trash item '%s'", tHandle)
             return False
         if theRoot.itemClass == nwItemClass.ARCHIVE:
-            logger.info("Not indexing archived item %s" % tHandle)
+            logger.info("Not indexing archived item '%s'", tHandle)
             return False
 
         itemClass  = theItem.itemClass
         itemLayout = theItem.itemLayout
 
-        logger.debug("Indexing item with handle %s" % tHandle)
+        logger.debug("Indexing item with handle '%s'", tHandle)
 
         # Check file type, and reset its old index
         # Also add a default entry T000000 in case the file has no title
@@ -457,11 +457,11 @@ class NWIndex():
         """
         isValid, theBits, _ = self.scanThis(aLine)
         if not isValid or len(theBits) < 2:
-            logger.warning("Skipping keyword with %d value(s) in %s" % (len(theBits), tHandle))
+            logger.warning("Skipping keyword with %d value(s) in '%s'", len(theBits), tHandle)
             return
 
         if theBits[0] not in nwKeyWords.VALID_KEYS:
-            logger.warning("Skipping invalid keyword '%s' in %s" % (theBits[0], tHandle))
+            logger.warning("Skipping invalid keyword '%s' in '%s'", theBits[0], tHandle)
             return
 
         sTitle = "T%06d" % nTitle
diff --git a/nw/core/item.py b/nw/core/item.py
index a7815f87..9da762c0 100644
--- a/nw/core/item.py
+++ b/nw/core/item.py
@@ -133,7 +133,7 @@ class NWItem():
                 # Sliently skip as we may otherwise cause orphaned
                 # items if an otherwise valid file is opened by a
                 # version of novelWriter that doesn't know the tag.
-                logger.error("Unknown tag '%s'" % xValue.tag)
+                logger.error("Unknown tag '%s'", xValue.tag)
 
         return True
 
@@ -205,7 +205,7 @@ class NWItem():
         elif isItemType(theType):
             self.itemType = nwItemType[theType]
         else:
-            logger.error("Unrecognised item type '%s'" % theType)
+            logger.error("Unrecognised item type '%s'", theType)
             self.itemType = nwItemType.NO_TYPE
         return
 
@@ -218,7 +218,7 @@ class NWItem():
         elif isItemClass(theClass):
             self.itemClass = nwItemClass[theClass]
         else:
-            logger.error("Unrecognised item class '%s'" % theClass)
+            logger.error("Unrecognised item class '%s'", theClass)
             self.itemClass = nwItemClass.NO_CLASS
         return
 
@@ -231,7 +231,7 @@ class NWItem():
         elif isItemLayout(theLayout):
             self.itemLayout = nwItemLayout[theLayout]
         else:
-            logger.error("Unrecognised item layout '%s'" % theLayout)
+            logger.error("Unrecognised item layout '%s'", theLayout)
             self.itemLayout = nwItemLayout.NO_LAYOUT
         return
 
diff --git a/nw/core/options.py b/nw/core/options.py
index bb1d9fbb..f89146c0 100644
--- a/nw/core/options.py
+++ b/nw/core/options.py
@@ -174,11 +174,11 @@ class OptionState():
         """Saves a value, with a given group and name.
         """
         if setGroup not in self.validMap:
-            logger.error("Unknown option group '%s'" % setGroup)
+            logger.error("Unknown option group '%s'", setGroup)
             return False
 
         if setName not in self.validMap[setGroup]:
-            logger.error("Unknown option name '%s'" % setName)
+            logger.error("Unknown option name '%s'", setName)
             return False
 
         if setGroup not in self.theState:
diff --git a/nw/core/project.py b/nw/core/project.py
index f2abd0dd..3a73fd03 100644
--- a/nw/core/project.py
+++ b/nw/core/project.py
@@ -369,7 +369,7 @@ class NWProject():
 
         self.clearProject()
         self.projPath = os.path.abspath(os.path.dirname(fileName))
-        logger.debug("Opening project: %s" % self.projPath)
+        logger.debug("Opening project: %s", self.projPath)
 
         # Standard Folders and Files
         # ==========================
@@ -385,7 +385,7 @@ class NWProject():
 
         legacyList = []  # Cleanup is done later
         for projItem in os.listdir(self.projPath):
-            logger.verbose("Project contains: %s" % projItem)
+            logger.verbose("Project contains: %s", projItem)
             if projItem.startswith("data_"):
                 legacyList.append(projItem)
 
@@ -442,8 +442,8 @@ class NWProject():
         hexVersion  = xRoot.attrib.get("hexVersion", "0x0")
         fileVersion = xRoot.attrib.get("fileVersion", self.tr("Unknown"))
 
-        logger.verbose("XML root is %s" % nwxRoot)
-        logger.verbose("File version is %s" % fileVersion)
+        logger.verbose("XML root is '%s'", nwxRoot)
+        logger.verbose("File version is '%s'", fileVersion)
 
         # Check File Type
         # ===============
@@ -503,13 +503,13 @@ class NWProject():
                     if xItem.text is None:
                         continue
                     if xItem.tag == "name":
-                        logger.verbose("Working Title: '%s'" % xItem.text)
+                        logger.verbose("Working Title: '%s'", xItem.text)
                         self.projName = xItem.text
                     elif xItem.tag == "title":
-                        logger.verbose("Title is '%s'" % xItem.text)
+                        logger.verbose("Title is '%s'", xItem.text)
                         self.bookTitle = xItem.text
                     elif xItem.tag == "author":
-                        logger.verbose("Author: '%s'" % xItem.text)
+                        logger.verbose("Author: '%s'", xItem.text)
                         self.bookAuthors.append(xItem.text)
                     elif xItem.tag == "saveCount":
                         self.saveCount = checkInt(xItem.text, 0)
@@ -610,7 +610,7 @@ class NWProject():
         if not self.ensureFolderStructure():
             return False
 
-        logger.debug("Saving project: %s" % self.projPath)
+        logger.debug("Saving project: %s", self.projPath)
 
         if autoSave:
             self.autoCount += 1
@@ -783,7 +783,7 @@ class NWProject():
         if not os.path.isdir(baseDir):
             try:
                 os.mkdir(baseDir)
-                logger.debug("Created folder %s" % baseDir)
+                logger.debug("Created folder: %s", baseDir)
             except Exception as e:
                 self.theParent.makeAlert([
                     self.tr("Could not create backup folder."), str(e)
@@ -805,7 +805,7 @@ class NWProject():
             self._clearLockFile()
             shutil.make_archive(baseName, "zip", self.projPath, ".")
             self._writeLockFile()
-            logger.info("Backup written to: %s" % archName)
+            logger.info("Backup written to: %s", archName)
             if doNotify:
                 self.theParent.makeAlert(self.tr(
                     "Backup archive file written to: {0}"
@@ -904,7 +904,7 @@ class NWProject():
             if not os.path.isdir(projPath):
                 try:
                     os.mkdir(projPath)
-                    logger.debug("Created folder %s" % projPath)
+                    logger.debug("Created folder: %s", projPath)
                 except Exception as e:
                     self.theParent.makeAlert([
                         self.tr("Could not create new project folder."), str(e)
@@ -1162,12 +1162,12 @@ class NWProject():
                 # Item's parent exists, but hasn't been sent yet, so add
                 # it again to the end, but make sure this doesn't get
                 # out hand, so we cap at 10000 items
-                logger.warning("Item %s found before its parent" % tHandle)
+                logger.warning("Item '%s' found before its parent", tHandle)
                 iterItems.append(tHandle)
                 nMax = min(len(iterItems), 10000)
             else:
                 # Item is orphaned
-                logger.error("Item %s has no parent in current tree" % tHandle)
+                logger.error("Item '%s' has no parent in current tree", tHandle)
                 tItem.setParent(None)
                 yield tItem
 
@@ -1221,7 +1221,7 @@ class NWProject():
         try:
             with open(loadFile, mode="r", encoding="utf8") as inFile:
                 self.langData = json.load(inFile)
-            logger.debug("Loaded project language file: %s" % os.path.basename(loadFile))
+            logger.debug("Loaded project language file: %s", os.path.basename(loadFile))
 
         except Exception:
             logger.error("Failed to project language file")
@@ -1299,7 +1299,7 @@ class NWProject():
         if not os.path.isdir(thePath):
             try:
                 os.mkdir(thePath)
-                logger.debug("Created folder %s" % thePath)
+                logger.debug("Created folder: %s", thePath)
             except Exception as e:
                 self.makeAlert([
                     self.tr("Could not create folder."), str(e)
@@ -1343,19 +1343,19 @@ class NWProject():
         orphanFiles = []
         for fileItem in os.listdir(self.projContent):
             if not fileItem.endswith(".nwd"):
-                logger.warning("Skipping file %s" % fileItem)
+                logger.warning("Skipping file: %s", fileItem)
                 continue
             if len(fileItem) != 17:
-                logger.warning("Skipping file %s" % fileItem)
+                logger.warning("Skipping file: %s", fileItem)
                 continue
             fHandle = fileItem[:13]
             if not isHandle(fHandle):
-                logger.warning("Skipping file %s" % fileItem)
+                logger.warning("Skipping file: %s", fileItem)
                 continue
             if fHandle in self.projTree:
-                logger.debug("Checking file %s, handle %s: OK" % (fileItem, fHandle))
+                logger.debug("Checking file %s, handle '%s': OK", fileItem, fHandle)
             else:
-                logger.warning("Checking file %s, handle %s: Orphaned" % (fileItem, fHandle))
+                logger.warning("Checking file %s, handle '%s': Orphaned", fileItem, fHandle)
                 orphanFiles.append(fHandle)
 
         # Report status
@@ -1436,7 +1436,7 @@ class NWProject():
         sessDiff = self.getSessionWordCount()
         sessTime = nowTime - self.projOpened
 
-        logger.info("The session lasted %d sec and added %d words" % (int(sessTime), sessDiff))
+        logger.info("The session lasted %d sec and added %d words", int(sessTime), sessDiff)
         if sessTime < 300 and sessDiff == 0:
             logger.info("Session too short, skipping log entry")
             return False
@@ -1478,7 +1478,7 @@ class NWProject():
             errList.append(self.tr("Not a folder: {0}").format(theData))
             return errList
 
-        logger.info("Old data folder %s found" % theFolder)
+        logger.info("Old data folder %s found", theFolder)
 
         # Move Documents to Content
         # =========================
@@ -1495,20 +1495,20 @@ class NWProject():
                 newPath = os.path.join(self.projContent, tHandle+".nwd")
                 try:
                     os.rename(theFile, newPath)
-                    logger.info("Moved file: %s" % theFile)
-                    logger.info("New location: %s" % newPath)
+                    logger.info("Moved file: %s", theFile)
+                    logger.info("New location: %s", newPath)
                 except Exception:
                     errList.append(self.tr("Could not move: {0}").format(theFile))
-                    logger.error("Could not move: %s" % theFile)
+                    logger.error("Could not move: %s", theFile)
                     nw.logException()
 
             elif len(dataItem) == 21 and dataItem.endswith("_main.bak"):
                 try:
                     os.unlink(theFile)
-                    logger.info("Deleted file: %s" % theFile)
+                    logger.info("Deleted file: %s", theFile)
                 except Exception:
                     errList.append(self.tr("Could not delete: {0}").format(theFile))
-                    logger.error("Could not delete: %s" % theFile)
+                    logger.error("Could not delete: %s", theFile)
                     nw.logException()
 
             else:
@@ -1520,10 +1520,10 @@ class NWProject():
         # ==================
         try:
             os.rmdir(theData)
-            logger.info("Deleted folder: %s" % theFolder)
+            logger.info("Deleted folder: %s", theFolder)
         except Exception:
             errList.append(self.tr("Could not delete: {0}").format(theFolder))
-            logger.error("Could not delete: %s" % theFolder)
+            logger.error("Could not delete: %s", theFolder)
             nw.logException()
 
         return errList
@@ -1541,9 +1541,9 @@ class NWProject():
 
         try:
             os.rename(theSrc, theDst)
-            logger.info("Moved to junk: %s" % theSrc)
+            logger.info("Moved to junk: %s", theSrc)
         except Exception:
-            logger.error("Could not move item %s to junk." % theSrc)
+            logger.error("Could not move item %s to junk", theSrc)
             nw.logException()
             return self.tr("Could not move item {0} to {1}.").format(theSrc, theJunk)
 
@@ -1574,11 +1574,11 @@ class NWProject():
 
         for rmFile in rmList:
             if os.path.isfile(rmFile):
-                logger.info("Deleting: %s" % rmFile)
+                logger.info("Deleting: %s", rmFile)
                 try:
                     os.unlink(rmFile)
                 except Exception:
-                    logger.error("Could not delete: %s" % rmFile)
+                    logger.error("Could not delete: %s", rmFile)
                     nw.logException()
                     return False
 
diff --git a/nw/core/spellcheck.py b/nw/core/spellcheck.py
index 9fcda88f..b24d027f 100644
--- a/nw/core/spellcheck.py
+++ b/nw/core/spellcheck.py
@@ -71,7 +71,7 @@ class NWSpellCheck():
                     outFile.write("%s\n" % newWord)
                 self.projDict.append(newWord)
             except Exception:
-                logger.error("Failed to add word to project word list %s" % str(self.projectDict))
+                logger.error("Failed to add word to project word list %s", str(self.projectDict))
                 nw.logException()
                 return False
             return True
@@ -111,7 +111,7 @@ class NWSpellCheck():
                     theLine = theLine.strip()
                     if len(theLine) > 0 and theLine not in self.projDict:
                         self.projDict.append(theLine)
-            logger.debug("Project word list contains %d words" % len(self.projDict))
+            logger.debug("Project word list contains %d words", len(self.projDict))
 
         except Exception:
             logger.error("Failed to load project word list")
@@ -149,10 +149,10 @@ class NWSpellEnchant(NWSpellCheck):
             self.theBroker = enchant.Broker()
             self.theDict = self.theBroker.request_dict(theLang)
             self.spellLanguage = theLang
-            logger.debug("Enchant spell checking for language %s loaded" % theLang)
+            logger.debug("Enchant spell checking for language '%s' loaded", theLang)
 
         except Exception:
-            logger.error("Failed to load enchant spell checking for language %s" % theLang)
+            logger.error("Failed to load enchant spell checking for language '%s'", theLang)
             self.theDict = FakeEnchant()
             self.spellLanguage = None
 
@@ -259,12 +259,12 @@ class NWSpellSimple(NWSpellCheck):
                         continue
                     self.theWords.add(theLine.strip().lower())
 
-            logger.debug("Spell check dictionary for language %s loaded" % theLang)
-            logger.debug("Dictionary contains %d words" % len(self.theWords))
+            logger.debug("Spell check dictionary for language '%s' loaded", theLang)
+            logger.debug("Dictionary contains %d words", len(self.theWords))
             self.spellLanguage = theLang
 
         except Exception:
-            logger.error("Failed to load spell check word list for language %s" % theLang)
+            logger.error("Failed to load spell check word list for language '%s'", theLang)
             nw.logException()
             self.spellLanguage = None
 
diff --git a/nw/core/toodt.py b/nw/core/toodt.py
index ba508f24..fe417371 100644
--- a/nw/core/toodt.py
+++ b/nw/core/toodt.py
@@ -644,7 +644,7 @@ class ToOdt(Tokenizer):
         """
         refStyle = self._mainPara.get(parName, None)
         if refStyle is None:
-            logger.error("Unknown paragraph style '%s'" % parName)
+            logger.error("Unknown paragraph style '%s'", parName)
             return "Standard"
 
         if not refStyle.checkNew(oStyle):
@@ -1295,5 +1295,5 @@ def _mkTag(nsName, tagName):
     theNS = XML_NS.get(nsName, "")
     if theNS:
         return "{%s}%s" % (theNS, tagName)
-    logger.warning("Missing xml namespace '%s'" % nsName)
+    logger.warning("Missing xml namespace '%s'", nsName)
     return tagName
diff --git a/nw/core/tree.py b/nw/core/tree.py
index 6393e42d..9539c986 100644
--- a/nw/core/tree.py
+++ b/nw/core/tree.py
@@ -111,24 +111,24 @@ class NWTree():
             tHandle = self._makeHandle()
 
         if tHandle in self._projTree:
-            logger.warning("Duplicate handle %s detected, skipping" % tHandle)
+            logger.warning("Duplicate handle '%s' detected, skipping", tHandle)
             return False
 
-        logger.verbose("Adding item %s with parent %s" % (str(tHandle), str(pHandle)))
+        logger.verbose("Adding item '%s' with parent '%s'", str(tHandle), str(pHandle))
 
         nwItem.setHandle(tHandle)
         nwItem.setParent(pHandle)
 
         if nwItem.itemType == nwItemType.ROOT:
-            logger.verbose("Item %s is a root item" % str(tHandle))
+            logger.verbose("Item '%s' is a root item", str(tHandle))
             self._treeRoots.append(tHandle)
             if nwItem.itemClass == nwItemClass.ARCHIVE:
-                logger.verbose("Item %s is the archive folder" % str(tHandle))
+                logger.verbose("Item '%s' is the archive folder", str(tHandle))
                 self._archRoot = tHandle
 
         if nwItem.itemType == nwItemType.TRASH:
             if self._trashRoot is None:
-                logger.verbose("Item %s is the trash folder" % str(tHandle))
+                logger.verbose("Item '%s' is the trash folder", str(tHandle))
                 self._trashRoot = tHandle
             else:
                 logger.error("Only one trash folder allowed")
@@ -245,9 +245,10 @@ class NWTree():
         if iLayout in LAYOUT_MAP:
             if hLevel in LAYOUT_MAP[iLayout]:
                 tItem.itemLayout = LAYOUT_MAP[iLayout][hLevel]
-                logger.debug("Changed layout for %s from %s to %s" % (
+                logger.debug(
+                    "Changed layout for %s from %s to %s",
                     tHandle, iLayout.name, tItem.itemLayout.name
-                ))
+                )
                 return True
 
         return False
@@ -357,13 +358,13 @@ class NWTree():
             if tHandle in self._projTree:
                 tmpOrder.append(tHandle)
             else:
-                logger.error("Handle %s in new tree order is not in project tree" % tHandle)
+                logger.error("Handle '%s' in new tree order is not in project tree", tHandle)
 
         # Do a reverse lookup to check for items that will be lost
         # This is mainly for debugging purposes
         for tHandle in self._treeOrder:
             if tHandle not in tmpOrder:
-                logger.warning("Handle %s in old tree order is not in new tree order" % tHandle)
+                logger.warning("Handle '%s' in old tree order is not in new tree order", tHandle)
 
         # Save the temp list
         self._treeOrder = tmpOrder
@@ -387,7 +388,7 @@ class NWTree():
         if tItem is None:
             return False
         if tItem.itemType != nwItemType.FILE:
-            logger.error("Item %s is not a file" % tHandle)
+            logger.error("Item %s is not a file", tHandle)
             return False
         if not isinstance(itemLayout, nwItemLayout):
             return False
@@ -444,7 +445,7 @@ class NWTree():
         """
         if tHandle in self._projTree:
             return self._projTree[tHandle]
-        logger.error("No tree item with handle %s" % str(tHandle))
+        logger.error("No tree item with handle '%s'", str(tHandle))
         return None
 
     def __delitem__(self, tHandle):
@@ -454,7 +455,7 @@ class NWTree():
             self._treeOrder.remove(tHandle)
             del self._projTree[tHandle]
         else:
-            logger.warning("Failed to delete item %s: item not found" % tHandle)
+            logger.warning("Failed to delete item '%s': item not found", tHandle)
             return
 
         if tHandle in self._treeRoots:
@@ -523,7 +524,7 @@ class NWTree():
             newSeed = str(self._handleSeed)
             self._handleSeed += 1
 
-        logger.verbose("Generating handle with seed '%s'" % newSeed)
+        logger.verbose("Generating handle with seed '%s'", newSeed)
         itemHandle = sha256(newSeed.encode()).hexdigest()[0:13]
         if itemHandle in self._projTree:
             logger.warning("Duplicate handle encountered! Retrying ...")
diff --git a/nw/dialogs/docsplit.py b/nw/dialogs/docsplit.py
index 219f1671..c6a57466 100644
--- a/nw/dialogs/docsplit.py
+++ b/nw/dialogs/docsplit.py
@@ -191,7 +191,7 @@ class GuiDocSplit(QDialog):
             srcItem.itemName, srcItem.itemClass, srcItem.itemParent
         )
         self.theParent.treeView.revealNewTreeItem(fHandle)
-        logger.verbose("Creating folder %s" % fHandle)
+        logger.verbose("Creating folder '%s'", fHandle)
 
         # Loop through, and create the files
         for wTitle, iStart, iEnd in finalOrder:
diff --git a/nw/error.py b/nw/error.py
index fee52ab7..16b91426 100644
--- a/nw/error.py
+++ b/nw/error.py
@@ -43,7 +43,7 @@ def logException():
     """Log the content of an exception message.
     """
     exType, exValue, _ = sys.exc_info()
-    logger.error("%s: %s" % (exType.__name__, str(exValue).strip("'")))
+    logger.error("%s: %s", exType.__name__, str(exValue).strip("'"))
 
 
 # =============================================================================================== #
@@ -159,7 +159,7 @@ def exceptionHandler(exType, exValue, exTrace):
     from traceback import print_tb
     from PyQt5.QtWidgets import qApp
 
-    logger.critical("%s: %s" % (exType.__name__, str(exValue)))
+    logger.critical("%s: %s", exType.__name__, str(exValue))
     print_tb(exTrace)
 
     try:
diff --git a/nw/gui/doceditor.py b/nw/gui/doceditor.py
index be521e70..a599fb83 100644
--- a/nw/gui/doceditor.py
+++ b/nw/gui/doceditor.py
@@ -343,7 +343,7 @@ class GuiDocEditor(QTextEdit):
 
         self._allowAutoReplace(True)
         afTime = time()
-        logger.debug("Document highlighted in %.3f ms" % (1000*(afTime-bfTime)))
+        logger.debug("Document highlighted in %.3f ms", 1000*(afTime-bfTime))
 
         self._lastEdit = time()
         self._lastActive = time()
@@ -438,9 +438,9 @@ class GuiDocEditor(QTextEdit):
 
         tHandle = self._nwItem.itemHandle
         if self._docHandle != tHandle:
-            logger.error("Editor handle %s and item handle %s do not match" % (
-                self._docHandle, tHandle
-            ))
+            logger.error(
+                "Editor handle '%s' and item handle '%s' do not match", self._docHandle, tHandle
+            )
             return False
 
         docText = self.getText()
@@ -656,7 +656,7 @@ class GuiDocEditor(QTextEdit):
             if theBlock:
                 self.setCursorPosition(theBlock.position())
                 self.docFooter.updateLineCount()
-                logger.verbose("Cursor moved to line %d" % theLine)
+                logger.verbose("Cursor moved to line %d", theLine)
 
         return True
 
@@ -703,7 +703,7 @@ class GuiDocEditor(QTextEdit):
         if not self._bigDoc:
             self.spellCheckDocument()
 
-        logger.verbose("Spell check is set to %s" % str(theMode))
+        logger.verbose("Spell check is set to '%s'", str(theMode))
 
         return True
 
@@ -723,7 +723,7 @@ class GuiDocEditor(QTextEdit):
                 self.hLight.rehighlight()
             qApp.restoreOverrideCursor()
             afTime = time()
-            logger.debug("Document highlighted in %.3f ms" % (1000*(afTime-bfTime)))
+            logger.debug("Document highlighted in %.3f ms", 1000*(afTime-bfTime))
             self.theParent.statusBar.setStatus(self.tr("Spell check complete"))
 
         return True
@@ -739,7 +739,7 @@ class GuiDocEditor(QTextEdit):
         passed to it without having to consider the internal logic of
         this class when calling these actions from other classes.
         """
-        logger.verbose("Requesting action: %s" % theAction.name)
+        logger.verbose("Requesting action: '%s'", theAction.name)
         if self._docHandle is None:
             logger.error("No document open")
             return False
@@ -798,7 +798,7 @@ class GuiDocEditor(QTextEdit):
         elif theAction == nwDocAction.INDENT_R:
             self._formatBlock(nwDocAction.INDENT_R)
         else:
-            logger.debug("Unknown or unsupported document action %s" % str(theAction))
+            logger.debug("Unknown or unsupported document action '%s'", str(theAction))
             self._allowAutoReplace(True)
             return False
 
@@ -871,15 +871,15 @@ class GuiDocEditor(QTextEdit):
         If the insert line is not blank, a new line is started.
         """
         if keyWord not in nwKeyWords.VALID_KEYS:
-            logger.error("Invalid keyword '%s'" % keyWord)
+            logger.error("Invalid keyword '%s'", keyWord)
             return False
 
-        logger.verbose("Inserting keyword '%s'" % keyWord)
+        logger.verbose("Inserting keyword '%s'", keyWord)
 
         theCursor = self.textCursor()
         theBlock = theCursor.block()
         if not theBlock.isValid():
-            logger.error("Failed to insert keyword '%s'" % keyWord)
+            logger.error("Failed to insert keyword '%s'", keyWord)
             return False
 
         theCursor.beginEditBlock()
@@ -1102,7 +1102,7 @@ class GuiDocEditor(QTextEdit):
             spellCheck &= theWord != ""
 
         if spellCheck:
-            logger.verbose("Looking up '%s' in the dictionary" % theWord)
+            logger.verbose("Looking up '%s' in the dictionary", theWord)
             spellCheck &= not self._theDict.checkWord(theWord)
 
         if spellCheck:
@@ -1154,7 +1154,7 @@ class GuiDocEditor(QTextEdit):
         wants to add a word to the project dictionary.
         """
         theWord = theCursor.selectedText().strip().strip(self._nonWord)
-        logger.debug("Added '%s' to project dictionary" % theWord)
+        logger.debug("Added '%s' to project dictionary", theWord)
         self._theDict.addWord(theWord)
         self.hLight.setDict(self._theDict)
         self.hLight.rehighlightBlock(theCursor.block())
@@ -1215,11 +1215,11 @@ class GuiDocEditor(QTextEdit):
                 QPointF(theSize.width(), theSize.height()), Qt.FuzzyHit
             )
             if self._queuePos <= thePos:
-                logger.verbose("Allowed cursor move to %d <= %d" % (self._queuePos, thePos))
+                logger.verbose("Allowed cursor move to %d <= %d", self._queuePos, thePos)
                 self.setCursorPosition(self._queuePos)
                 self._queuePos = None
             else:
-                logger.verbose("Denied cursor move to %d > %d" % (self._queuePos, thePos))
+                logger.verbose("Denied cursor move to %d > %d", self._queuePos, thePos)
         return
 
     ##
@@ -1350,9 +1350,10 @@ class GuiDocEditor(QTextEdit):
             theCursor.endEditBlock()
             theCursor.setPosition(theCursor.selectionEnd())
             self.setTextCursor(theCursor)
-            logger.verbose("Replaced occurrence of '%s' with '%s' on line %d" % (
+            logger.verbose(
+                "Replaced occurrence of '%s' with '%s' on line %d",
                 searchFor, replWith, theCursor.blockNumber()
-            ))
+            )
         else:
             logger.error("The selected text is not a search result, skipping replace")
 
@@ -1390,10 +1391,10 @@ class GuiDocEditor(QTextEdit):
                 return False
 
             if loadTag:
-                logger.verbose("Attempting to follow tag '%s'" % theWord)
+                logger.verbose("Attempting to follow tag '%s'", theWord)
                 self.theParent.docViewer.loadFromTag(theWord)
             else:
-                logger.verbose("Potential tag '%s'" % theWord)
+                logger.verbose("Potential tag '%s'", theWord)
 
             return True
 
@@ -1713,12 +1714,12 @@ class GuiDocEditor(QTextEdit):
         theCursor = self.textCursor()
         theBlock = theCursor.block()
         if not theBlock.isValid():
-            logger.debug("Invalid block selected for action %s" % str(docAction))
+            logger.debug("Invalid block selected for action '%s'", str(docAction))
             return False
 
         theText = theBlock.text()
         if len(theText.strip()) == 0:
-            logger.debug("Empty block selected for action %s" % str(docAction))
+            logger.debug("Empty block selected for action '%s'", str(docAction))
             return False
 
         # Remove existing format first, if any
@@ -1805,7 +1806,7 @@ class GuiDocEditor(QTextEdit):
         elif docAction == nwDocAction.BLOCK_TXT:
             theText = newText
         else:
-            logger.error("Unknown or unsupported block format requested: %s" % str(docAction))
+            logger.error("Unknown or unsupported block format requested: '%s'", str(docAction))
             return False
 
         # Replace the block text
@@ -2208,7 +2209,7 @@ class GuiDocEditSearch(QFrame):
         self.searchBox.selectAll()
         if self.isRegEx:
             self._alertSearchValid(True)
-        logger.verbose("Setting search text to '%s'" % theText)
+        logger.verbose("Setting search text to '%s'", theText)
         return True
 
     def setReplaceText(self, theText):
diff --git a/nw/gui/docviewer.py b/nw/gui/docviewer.py
index f82e98f8..e6417b8c 100644
--- a/nw/gui/docviewer.py
+++ b/nw/gui/docviewer.py
@@ -167,7 +167,7 @@ class GuiDocViewer(QTextBrowser):
         if tItem.itemType != nwItemType.FILE:
             return False
 
-        logger.debug("Generating preview for item %s" % tHandle)
+        logger.debug("Generating preview for item '%s'", tHandle)
         qApp.setOverrideCursor(QCursor(Qt.WaitCursor))
 
         sPos = self.verticalScrollBar().value()
@@ -185,7 +185,7 @@ class GuiDocViewer(QTextBrowser):
             aDoc.doConvert()
             aDoc.doPostProcessing()
         except Exception:
-            logger.error("Failed to generate preview for document with handle '%s'" % tHandle)
+            logger.error("Failed to generate preview for document with handle '%s'", tHandle)
             nw.logException()
             self.setText(self.tr("An error occurred while generating the preview."))
 
@@ -243,7 +243,7 @@ class GuiDocViewer(QTextBrowser):
         tag rather than a known handle. This function depends on the
         index being up to date.
         """
-        logger.debug("Loading document from tag '%s'" % theTag)
+        logger.debug("Loading document from tag '%s'", theTag)
         tHandle, _, sTitle = self.theParent.theIndex.getTagSource(theTag)
         if tHandle is None:
             self.theParent.makeAlert(self.tr(
@@ -258,7 +258,7 @@ class GuiDocViewer(QTextBrowser):
             # Let the parent handle the opening as it also ensures that
             # the doc view panel is visible in case this request comes
             # from outside this class.
-            logger.verbose("Tag points to %s#%s" % (tHandle, sTitle))
+            logger.verbose("Tag points to '%s#%s'", tHandle, sTitle)
             self.theParent.viewDocument(tHandle, "#%s" % sTitle)
         return True
 
@@ -266,7 +266,7 @@ class GuiDocViewer(QTextBrowser):
         """Wrapper function for various document actions on the current
         document.
         """
-        logger.verbose("Requesting action: %s" % theAction.name)
+        logger.verbose("Requesting action: '%s'", theAction.name)
         if self._docHandle is None:
             logger.error("No document open")
             return False
@@ -279,7 +279,7 @@ class GuiDocViewer(QTextBrowser):
         elif theAction == nwDocAction.SEL_PARA:
             self._makeSelection(QTextCursor.BlockUnderCursor)
         else:
-            logger.debug("Unknown or unsupported document action %s" % str(theAction))
+            logger.debug("Unknown or unsupported document action '%s'", str(theAction))
             return False
         return True
 
@@ -289,7 +289,7 @@ class GuiDocViewer(QTextBrowser):
         if not isinstance(tAnchor, str):
             return False
         if tAnchor.startswith("#"):
-            logger.verbose("Moving to anchor %s" % tAnchor)
+            logger.verbose("Moving to anchor '%s'", tAnchor)
             self.setSource(QUrl(tAnchor))
         return True
 
@@ -378,7 +378,7 @@ class GuiDocViewer(QTextBrowser):
             theBlock = self._qDocument.findBlockByLineNumber(theLine)
             if theBlock:
                 self.setCursorPosition(theBlock.position())
-                logger.verbose("Cursor moved to line %d" % theLine)
+                logger.verbose("Cursor moved to line %d", theLine)
         return True
 
     def setScrollPosition(self, thePos):
@@ -410,7 +410,7 @@ class GuiDocViewer(QTextBrowser):
         """Slot for a link in the document being clicked.
         """
         theLink = theURL.url()
-        logger.verbose("Clicked link: '%s'" % theLink)
+        logger.verbose("Clicked link: '%s'", theLink)
         if len(theLink) > 0:
             theBits = theLink.split("=")
             if len(theBits) == 2:
@@ -617,7 +617,7 @@ class GuiDocViewHistory():
 
         self._dumpHistory()
 
-        logger.verbose("Added %s to view history" % tHandle)
+        logger.verbose("Added '%s' to view history", tHandle)
 
         return True
 
@@ -1114,7 +1114,7 @@ class GuiDocViewFooter(QWidget):
     def _doToggleSticky(self, theState):
         """Toggle the sticky flag for the reference panel.
         """
-        logger.verbose("Reference sticky is %s" % str(theState))
+        logger.verbose("Reference sticky is %s", str(theState))
         self.docViewer.stickyRef = theState
         if not theState and self.docViewer.docHandle() is not None:
             self.viewMeta.refreshReferences(self.docViewer.docHandle())
@@ -1210,7 +1210,7 @@ class GuiDocViewDetails(QScrollArea):
         """Capture the link-click and forward it to the document viewer
         class for handling.
         """
-        logger.verbose("Clicked link: '%s'" % theLink)
+        logger.verbose("Clicked link: '%s'", theLink)
         if len(theLink) == 21:
             tHandle = theLink[:13]
             tAnchor = theLink[13:]
diff --git a/nw/gui/noveltree.py b/nw/gui/noveltree.py
index dad63610..ec7187c2 100644
--- a/nw/gui/noveltree.py
+++ b/nw/gui/noveltree.py
@@ -222,7 +222,7 @@ class GuiNovelTree(QTreeWidget):
         tHandle = theData[0]
         tLine = checkInt(theData[1], 1)
 
-        logger.verbose("User selected entry with handle %s on line %s" % (tHandle, tLine))
+        logger.verbose("User selected entry with handle '%s' on line %s", tHandle, tLine)
         self.theParent.openDocument(tHandle, tLine=tLine-1, doScroll=True)
 
         return
diff --git a/nw/gui/outline.py b/nw/gui/outline.py
index 62a328c2..0f91d9c2 100644
--- a/nw/gui/outline.py
+++ b/nw/gui/outline.py
@@ -212,7 +212,7 @@ class GuiOutline(QTreeWidget):
         except Exception:
             tLine = 1
 
-        logger.verbose("User selected entry with handle %s on line %s" % (tHandle, tLine))
+        logger.verbose("User selected entry with handle '%s' on line %s", tHandle, tLine)
         self.theParent.openDocument(tHandle, tLine=tLine-1, doScroll=True)
 
         return
@@ -248,7 +248,7 @@ class GuiOutline(QTreeWidget):
         """Receive the changes to column visibility forwarded by the
         header context menu.
         """
-        logger.verbose("User toggled Outline column '%s'" % theItem.name)
+        logger.verbose("User toggled Outline column '%s'", theItem.name)
         if theItem in self.colIndex:
             self.setColumnHidden(self.colIndex[theItem], not isChecked)
             self._saveHeaderState()
@@ -272,7 +272,7 @@ class GuiOutline(QTreeWidget):
             try:
                 treeOrder.append(nwOutline[hName])
             except Exception:
-                logger.warning("Ignored unknown outline column '%s'" % str(hName))
+                logger.warning("Ignored unknown outline column '%s'", str(hName))
 
         # Add columns that was not in the file to the treeOrder array.
         for hItem in nwOutline:
@@ -285,7 +285,7 @@ class GuiOutline(QTreeWidget):
             self.treeOrder = treeOrder
         else:
             logger.error("Failed to extract outline column order from previous session")
-            logger.error("Column count doesn't match %d != %d" % (len(treeOrder), self.treeNCols))
+            logger.error("Column count doesn't match %d != %d", len(treeOrder), self.treeNCols)
 
         # We load whatever column widths and hidden states we find in
         # the file, and leave the rest in their default state.
@@ -294,14 +294,14 @@ class GuiOutline(QTreeWidget):
             try:
                 self.colWidth[nwOutline[hName]] = self.mainConf.pxInt(tmpWidth[hName])
             except Exception:
-                logger.warning("Ignored unknown outline column '%s'" % str(hName))
+                logger.warning("Ignored unknown outline column '%s'", str(hName))
 
         tmpHidden = self.optState.getValue("GuiOutline", "columnHidden", {})
         for hName in tmpHidden:
             try:
                 self.colHidden[nwOutline[hName]] = tmpHidden[hName]
             except Exception:
-                logger.warning("Ignored unknown outline column '%s'" % str(hName))
+                logger.warning("Ignored unknown outline column '%s'", str(hName))
 
         self.headerMenu.setHiddenState(self.colHidden)
 
diff --git a/nw/gui/outlinedetails.py b/nw/gui/outlinedetails.py
index 3566d1da..97a7d03e 100644
--- a/nw/gui/outlinedetails.py
+++ b/nw/gui/outlinedetails.py
@@ -323,7 +323,7 @@ class GuiOutlineDetails(QScrollArea):
     def _tagClicked(self, theLink):
         """Capture the click of a tag in the right-most column.
         """
-        logger.verbose("Clicked link: '%s'" % theLink)
+        logger.verbose("Clicked link: '%s'", theLink)
         if len(theLink) > 0:
             theBits = theLink.split("=")
             if len(theBits) == 2:
diff --git a/nw/gui/projtree.py b/nw/gui/projtree.py
index c9dbc49e..da8de118 100644
--- a/nw/gui/projtree.py
+++ b/nw/gui/projtree.py
@@ -207,8 +207,9 @@ class GuiProjectTree(QTreeWidget):
             return False
 
         # Everything is fine, we have what we need, so we proceed
-        logger.verbose("Adding new item of type %s and class %s to handle %s" % (
-            itemType.name, itemClass.name, str(pHandle))
+        logger.verbose(
+            "Adding new item of type '%s' and class '%s' to handle '%s'",
+            itemType.name, itemClass.name, str(pHandle)
         )
 
         if itemType == nwItemType.ROOT:
@@ -454,7 +455,7 @@ class GuiProjectTree(QTreeWidget):
         if not msgYes:
             return False
 
-        logger.verbose("Deleting %d file(s) from Trash" % nTrash)
+        logger.verbose("Deleting %d file(s) from Trash", nTrash)
         for tHandle in self.getTreeFromHandle(trashHandle):
             if tHandle == trashHandle:
                 continue
@@ -496,7 +497,7 @@ class GuiProjectTree(QTreeWidget):
 
         wCount = int(trItemS.data(self.C_COUNT, Qt.UserRole))
         if nwItemS.itemType == nwItemType.FILE:
-            logger.debug("User requested file %s deleted" % tHandle)
+            logger.debug("User requested file '%s' deleted", tHandle)
             trItemP = trItemS.parent()
             trItemT = self._addTrashRoot()
             if trItemP is None or trItemT is None:
@@ -519,7 +520,7 @@ class GuiProjectTree(QTreeWidget):
                     doPermanent = True
 
                 if doPermanent:
-                    logger.debug("Permanently deleting file with handle %s" % tHandle)
+                    logger.debug("Permanently deleting file with handle '%s'", tHandle)
 
                     self.propagateCount(tHandle, 0)
                     tIndex = trItemP.indexOfChild(trItemS)
@@ -551,7 +552,7 @@ class GuiProjectTree(QTreeWidget):
                     if pHandle is None:
                         logger.warning("File has no parent item")
 
-                    logger.debug("Moving file %s to trash" % tHandle)
+                    logger.debug("Moving file '%s' to trash", tHandle)
 
                     self.propagateCount(tHandle, 0)
                     tIndex  = trItemP.indexOfChild(trItemS)
@@ -565,7 +566,7 @@ class GuiProjectTree(QTreeWidget):
                     self._setTreeChanged(True)
 
         elif nwItemS.itemType == nwItemType.FOLDER:
-            logger.debug("User requested folder %s deleted" % tHandle)
+            logger.debug("User requested folder '%s' deleted", tHandle)
             trItemP = trItemS.parent()
             if trItemP is None:
                 logger.error("Could not delete folder")
@@ -584,7 +585,7 @@ class GuiProjectTree(QTreeWidget):
                 return False
 
         elif nwItemS.itemType == nwItemType.ROOT:
-            logger.debug("User requested root folder %s deleted" % tHandle)
+            logger.debug("User requested root folder '%s' deleted", tHandle)
             tIndex = self.indexOfTopLevelItem(trItemS)
             if trItemS.childCount() == 0:
                 self.takeTopLevelItem(tIndex)
@@ -695,7 +696,7 @@ class GuiProjectTree(QTreeWidget):
             iCount += 1
             self._addTreeItem(nwItem)
 
-        logger.debug("%d items added to the project tree" % iCount)
+        logger.debug("%d item(s) added to the project tree", iCount)
         return True
 
     def undoLastMove(self):
@@ -724,9 +725,7 @@ class GuiProjectTree(QTreeWidget):
         wCount = int(srcItem.data(self.C_COUNT, Qt.UserRole))
         sHandle = srcItem.data(self.C_NAME, Qt.UserRole)
         dHandle = dstItem.data(self.C_NAME, Qt.UserRole)
-        logger.debug("Moving item %s back to %s, index %d" % (
-            sHandle, dHandle, dstIndex
-        ))
+        logger.debug("Moving item '%s' back to '%s', index %d", sHandle, dHandle, dstIndex)
 
         self.propagateCount(sHandle, 0)
         parItem = srcItem.parent()
@@ -882,7 +881,7 @@ class GuiProjectTree(QTreeWidget):
         allowDrop &= not (self.dropIndicatorPosition() == QAbstractItemView.OnItem and onFile)
 
         if allowDrop and not isRoot:
-            logger.debug("Drag'n'drop of item %s accepted" % sHandle)
+            logger.debug("Drag'n'drop of item '%s' accepted", sHandle)
             self.propagateCount(sHandle, 0)
             QTreeWidget.dropEvent(self, theEvent)
             self._postItemMove(sHandle, snItem, dnItem, wCount)
@@ -890,7 +889,7 @@ class GuiProjectTree(QTreeWidget):
 
         else:
             theEvent.ignore()
-            logger.debug("Drag'n'drop of item %s not accepted" % sHandle)
+            logger.debug("Drag'n'drop of item '%s' not accepted", sHandle)
             self.makeAlert(self.tr(
                 "The item cannot be moved to that location."
             ), nwAlert.ERROR)
@@ -913,9 +912,10 @@ class GuiProjectTree(QTreeWidget):
         # If the item does not have the same class as the target,
         # and the target is not a free root folder, update its class
         if not (isSame or onFree):
-            logger.debug("Item %s class has been changed from %s to %s" % (
+            logger.debug(
+                "Item '%s' class has been changed from '%s' to '%s'",
                 sHandle, snItem.itemClass.name, dnItem.itemClass.name
-            ))
+            )
             snItem.setClass(dnItem.itemClass)
             self.setTreeItemValues(sHandle)
 
@@ -1002,7 +1002,7 @@ class GuiProjectTree(QTreeWidget):
                 try:
                     byIndex = self._treeMap[pHandle].indexOfChild(self._treeMap[nHandle])
                 except Exception:
-                    logger.error("Failed to get index of item with handle %s" % nHandle)
+                    logger.error("Failed to get index of item with handle '%s'", nHandle)
             if byIndex >= 0:
                 self._treeMap[pHandle].insertChild(byIndex+1, newItem)
             else:
@@ -1052,14 +1052,14 @@ class GuiProjectTree(QTreeWidget):
         nwItemS = self.theProject.projTree[tHandle]
         trItemP = trItemS.parent()
         if trItemP is None:
-            logger.error("Failed to find new parent item of %s" % tHandle)
+            logger.error("Failed to find new parent item of '%s'", tHandle)
             return False
 
         pHandle = trItemP.data(self.C_NAME, Qt.UserRole)
         nwItemS.setParent(pHandle)
         self.setTreeItemValues(tHandle)
 
-        logger.debug("The parent of item %s has been changed to %s" % (tHandle, pHandle))
+        logger.debug("The parent of item '%s' has been changed to '%s'", tHandle, pHandle)
 
         return True
 
diff --git a/nw/gui/theme.py b/nw/gui/theme.py
index 9e5888ec..c3ee1f24 100644
--- a/nw/gui/theme.py
+++ b/nw/gui/theme.py
@@ -134,8 +134,8 @@ class GuiTheme:
         self.guiDPI = qApp.primaryScreen().logicalDotsPerInchX()
         self.guiScale = qApp.primaryScreen().logicalDotsPerInchX()/96.0
         self.mainConf.guiScale = self.guiScale
-        logger.verbose("GUI DPI: %.1f" % self.guiDPI)
-        logger.verbose("GUI Scale: %.2f" % self.guiScale)
+        logger.verbose("GUI DPI: %.1f", self.guiDPI)
+        logger.verbose("GUI Scale: %.2f", self.guiScale)
 
         # Fonts
         self.guiFont = qApp.font()
@@ -152,12 +152,12 @@ class GuiTheme:
         self.guiFontFixed.setPointSizeF(0.95*self.fontPointSize)
         self.guiFontFixed.setFamily(QFontDatabase.systemFont(QFontDatabase.FixedFont).family())
 
-        logger.verbose("GUI Font Family: %s" % self.guiFont.family())
-        logger.verbose("GUI Font Point Size: %.2f" % self.fontPointSize)
-        logger.verbose("GUI Font Pixel Size: %d" % self.fontPixelSize)
-        logger.verbose("GUI Base Icon Size: %d" % self.baseIconSize)
-        logger.verbose("Text 'N' Height: %d" % self.textNHeight)
-        logger.verbose("Text 'N' Width: %d" % self.textNWidth)
+        logger.verbose("GUI Font Family: %s", self.guiFont.family())
+        logger.verbose("GUI Font Point Size: %.2f", self.fontPointSize)
+        logger.verbose("GUI Font Pixel Size: %d", self.fontPixelSize)
+        logger.verbose("GUI Base Icon Size: %d", self.baseIconSize)
+        logger.verbose("Text 'N' Height: %d", self.textNHeight)
+        logger.verbose("Text 'N' Width: %d", self.textNWidth)
 
         # Internal Mapping
         self.makeAlert = self.theParent.makeAlert
@@ -192,7 +192,7 @@ class GuiTheme:
         for fontFam in os.listdir(fontAssets):
             fontDir = os.path.join(fontAssets, fontFam)
             if os.path.isdir(fontDir):
-                logger.verbose("Found font: %s" % fontFam)
+                logger.verbose("Found font: %s", fontFam)
                 if fontFam not in self.guiFontDB.families():
                     for fontFile in os.listdir(fontDir):
                         ttfFile = os.path.join(fontDir, fontFile)
@@ -201,10 +201,10 @@ class GuiTheme:
 
         for ttfFile in ttfList:
             relPath = os.path.relpath(ttfFile, fontAssets)
-            logger.verbose("Adding font: %s" % relPath)
+            logger.verbose("Adding font: %s", relPath)
             fontID = self.guiFontDB.addApplicationFont(ttfFile)
             if fontID < 0:
-                logger.error("Failed to add font: %s" % relPath)
+                logger.error("Failed to add font: %s", relPath)
 
         return
 
@@ -266,7 +266,7 @@ class GuiTheme:
         """Load the currently specified GUI theme.
         """
         logger.debug("Loading theme files")
-        logger.debug("System icon theme is '%s'" % str(QIcon.themeName()))
+        logger.debug("System icon theme is '%s'", str(QIcon.themeName()))
 
         # CSS File
         cssData = ""
@@ -285,7 +285,7 @@ class GuiTheme:
             with open(self.confFile, mode="r", encoding="utf8") as inFile:
                 confParser.read_file(inFile)
         except Exception:
-            logger.error("Could not load theme settings from: %s" % self.confFile)
+            logger.error("Could not load theme settings from: %s", self.confFile)
             nw.logException()
             return False
 
@@ -329,7 +329,7 @@ class GuiTheme:
         qApp.setStyleSheet(cssData)
         qApp.setPalette(self.guiPalette)
 
-        logger.info("Loaded theme '%s'" % self.guiTheme)
+        logger.info("Loaded theme '%s'", self.guiTheme)
 
         return True
 
@@ -343,7 +343,7 @@ class GuiTheme:
             with open(self.syntaxFile, mode="r", encoding="utf8") as inFile:
                 confParser.read_file(inFile)
         except Exception:
-            logger.error("Could not load syntax colours from: %s" % self.syntaxFile)
+            logger.error("Could not load syntax colours from: %s", self.syntaxFile)
             nw.logException()
             return False
 
@@ -378,7 +378,7 @@ class GuiTheme:
             self.colRepTag = self._loadColour(confParser, cnfSec, "replacetag")
             self.colMod    = self._loadColour(confParser, cnfSec, "modifier")
 
-        logger.info("Loaded syntax theme '%s'" % self.guiSyntax)
+        logger.info("Loaded syntax theme '%s'", self.guiSyntax)
 
         return True
 
@@ -393,7 +393,7 @@ class GuiTheme:
             themeConf = os.path.join(
                 self.mainConf.themeRoot, self.guiPath, themeDir, self.confName
             )
-            logger.verbose("Checking theme config for '%s'" % themeDir)
+            logger.verbose("Checking theme config for '%s'", themeDir)
             try:
                 with open(themeConf, mode="r", encoding="utf8") as inFile:
                     confParser.read_file(inFile)
@@ -406,7 +406,7 @@ class GuiTheme:
             if confParser.has_section("Main"):
                 if confParser.has_option("Main", "name"):
                     themeName = confParser.get("Main", "name")
-                    logger.verbose("Theme name is '%s'" % themeName)
+                    logger.verbose("Theme name is '%s'", themeName)
             if themeName != "":
                 self.themeList.append((themeDir, themeName))
 
@@ -426,7 +426,7 @@ class GuiTheme:
             syntaxPath = os.path.join(syntaxDir, syntaxFile)
             if not os.path.isfile(syntaxPath):
                 continue
-            logger.verbose("Checking theme syntax for '%s'" % syntaxFile)
+            logger.verbose("Checking theme syntax for '%s'", syntaxFile)
             try:
                 with open(syntaxPath, mode="r", encoding="utf8") as inFile:
                     confParser.read_file(inFile)
@@ -441,7 +441,7 @@ class GuiTheme:
                     syntaxName = confParser.get("Main", "name")
             if len(syntaxFile) > 5 and syntaxName != "":
                 self.syntaxList.append((syntaxFile[:-5], syntaxName))
-                logger.verbose("Syntax name is '%s'" % syntaxName)
+                logger.verbose("Syntax name is '%s'", syntaxName)
 
         self.syntaxList = sorted(self.syntaxList, key=lambda x: x[1])
 
@@ -462,10 +462,10 @@ class GuiTheme:
                 outData.append(int(inData[1]))
                 outData.append(int(inData[2]))
             except Exception:
-                logger.error("Could not load theme colours for '%s' from config file" % cnfName)
+                logger.error("Could not load theme colours for '%s' from config file", cnfName)
                 outData = [0, 0, 0]
         else:
-            logger.warning("Could not find theme colours for '%s' in config file" % cnfName)
+            logger.warning("Could not find theme colours for '%s' in config file", cnfName)
             outData = [0, 0, 0]
         return outData
 
@@ -480,7 +480,7 @@ class GuiTheme:
                 readCol.append(int(inData[1]))
                 readCol.append(int(inData[2]))
             except Exception:
-                logger.error("Could not load theme colours for '%s' from config file" % cnfName)
+                logger.error("Could not load theme colours for '%s' from config file", cnfName)
                 return
         if len(readCol) == 3:
             self.guiPalette.setColor(paletteVal, QColor(*readCol))
@@ -637,7 +637,7 @@ class GuiIcons:
         self.themeMap = {}
         checkPath = os.path.join(self.mainConf.iconPath, self.mainConf.guiIcons)
         if os.path.isdir(checkPath):
-            logger.debug("Loading icon theme '%s'" % self.mainConf.guiIcons)
+            logger.debug("Loading icon theme '%s'", self.mainConf.guiIcons)
             self.iconPath = checkPath
             self.confFile = os.path.join(checkPath, self.confName)
         else:
@@ -649,7 +649,7 @@ class GuiIcons:
             with open(self.confFile, mode="r", encoding="utf8") as inFile:
                 confParser.read_file(inFile)
         except Exception:
-            logger.error("Could not load icon theme settings from: %s" % self.confFile)
+            logger.error("Could not load icon theme settings from: %s", self.confFile)
             nw.logException()
             return False
 
@@ -669,16 +669,16 @@ class GuiIcons:
         if confParser.has_section(cnfSec):
             for iconName, iconFile in confParser.items(cnfSec):
                 if iconName not in self.ICON_MAP:
-                    logger.error("Unknown icon name '%s' in config file" % iconName)
+                    logger.error("Unknown icon name '%s' in config file", iconName)
                 else:
                     iconPath = os.path.join(self.iconPath, iconFile)
                     if os.path.isfile(iconPath):
                         self.themeMap[iconName] = iconPath
-                        logger.verbose("Icon slot '%s' using file '%s'" % (iconName, iconFile))
+                        logger.verbose("Icon slot '%s' using file '%s'", iconName, iconFile)
                     else:
-                        logger.error("Icon file '%s' not in theme folder" % iconFile)
+                        logger.error("Icon file '%s' not in theme folder", iconFile)
 
-        logger.info("Loaded icon theme '%s'" % self.mainConf.guiIcons)
+        logger.info("Loaded icon theme '%s'", self.mainConf.guiIcons)
 
         return True
 
@@ -691,14 +691,14 @@ class GuiIcons:
         map. This function always returns a QSwgWidget.
         """
         if decoKey not in self.DECO_MAP:
-            logger.error("Decoration with name '%s' does not exist" % decoKey)
+            logger.error("Decoration with name '%s' does not exist", decoKey)
             return QPixmap()
 
         imgPath = os.path.join(
             self.mainConf.assetPath, "images", self.DECO_MAP[decoKey]
         )
         if not os.path.isfile(imgPath):
-            logger.error("Decoration file '%s' not in assets folder" % self.DECO_MAP[decoKey])
+            logger.error("Decoration file '%s' not in assets folder", self.DECO_MAP[decoKey])
             return QPixmap()
 
         theDeco = QPixmap(imgPath)
@@ -742,7 +742,7 @@ class GuiIcons:
             if not os.path.isdir(themePath) or themeDir == self.fbackName:
                 continue
             themeConf = os.path.join(themePath, self.confName)
-            logger.verbose("Checking icon theme config for '%s'" % themeDir)
+            logger.verbose("Checking icon theme config for '%s'", themeDir)
             try:
                 with open(themeConf, mode="r", encoding="utf8") as inFile:
                     confParser.read_file(inFile)
@@ -755,7 +755,7 @@ class GuiIcons:
             if confParser.has_section("Main"):
                 if confParser.has_option("Main", "name"):
                     themeName = confParser.get("Main", "name")
-                    logger.verbose("Theme name is '%s'" % themeName)
+                    logger.verbose("Theme name is '%s'", themeName)
             if themeName != "":
                 self.themeList.append((themeDir, themeName))
 
@@ -774,7 +774,7 @@ class GuiIcons:
         a QIcon.
         """
         if iconKey not in self.ICON_MAP:
-            logger.error("Requested unknown icon name '%s'" % iconKey)
+            logger.error("Requested unknown icon name '%s'", iconKey)
             return QIcon()
 
         # If we just want the app icon, return it right away
@@ -785,17 +785,17 @@ class GuiIcons:
         # First in the theme folder
         if iconKey in self.themeMap:
             relPath = os.path.relpath(self.themeMap[iconKey], self.mainConf.iconPath)
-            logger.verbose("Loading: %s" % relPath)
+            logger.verbose("Loading: %s", relPath)
             return QIcon(self.themeMap[iconKey])
 
         # Next, we try to load the Qt style icons
         if self.ICON_MAP[iconKey][0] is not None:
-            logger.verbose("Loading icon '%s' from Qt QStyle.standardIcon" % iconKey)
+            logger.verbose("Loading icon '%s' from Qt QStyle.standardIcon", iconKey)
             return qApp.style().standardIcon(self.ICON_MAP[iconKey][0])
 
         # If we're still here, try to set from system theme
         if self.ICON_MAP[iconKey][1] is not None:
-            logger.verbose("Loading icon '%s' from system theme" % iconKey)
+            logger.verbose("Loading icon '%s' from system theme", iconKey)
             if QIcon().hasThemeIcon(self.ICON_MAP[iconKey][1]):
                 return QIcon().fromTheme(self.ICON_MAP[iconKey][1])
 
@@ -805,16 +805,16 @@ class GuiIcons:
                 self.mainConf.iconPath, self.fbackName, "%s-dark.svg" % iconKey
             )
             if os.path.isfile(fbackIcon):
-                logger.verbose("Loading icon '%s' from fallback theme (dark mode)" % iconKey)
+                logger.verbose("Loading icon '%s' from fallback theme (dark mode)", iconKey)
                 return QIcon(fbackIcon)
 
         fbackIcon = os.path.join(self.mainConf.iconPath, self.fbackName, "%s.svg" % iconKey)
         if os.path.isfile(fbackIcon):
-            logger.verbose("Loading icon '%s' from fallback theme (light mode)" % iconKey)
+            logger.verbose("Loading icon '%s' from fallback theme (light mode)", iconKey)
             return QIcon(fbackIcon)
 
         # Give up and return an empty icon
-        logger.warning("Did not load an icon for '%s'" % iconKey)
+        logger.warning("Did not load an icon for '%s'", iconKey)
 
         return QIcon()
 
diff --git a/nw/guimain.py b/nw/guimain.py
index 337d2904..76e725e2 100644
--- a/nw/guimain.py
+++ b/nw/guimain.py
@@ -68,19 +68,19 @@ class GuiMain(QMainWindow):
         # System Info
         # ===========
 
-        logger.info("OS: %s" % self.mainConf.osType)
-        logger.info("Kernel: %s" % self.mainConf.kernelVer)
-        logger.info("Host: %s" % self.mainConf.hostName)
-        logger.info("Qt5 Version: %s (%d)" % (
-            self.mainConf.verQtString, self.mainConf.verQtValue)
+        logger.info("OS: %s", self.mainConf.osType)
+        logger.info("Kernel: %s", self.mainConf.kernelVer)
+        logger.info("Host: %s", self.mainConf.hostName)
+        logger.info(
+            "Qt5 Version: %s (%d)", self.mainConf.verQtString, self.mainConf.verQtValue
         )
-        logger.info("PyQt5 Version: %s (%d)" % (
-            self.mainConf.verPyQtString, self.mainConf.verPyQtValue)
+        logger.info(
+            "PyQt5 Version: %s (%d)", self.mainConf.verPyQtString, self.mainConf.verPyQtValue
         )
-        logger.info("Python Version: %s (0x%x)" % (
-            self.mainConf.verPyString, self.mainConf.verPyHexVal)
+        logger.info(
+            "Python Version: %s (0x%x)", self.mainConf.verPyString, self.mainConf.verPyHexVal
         )
-        logger.info("GUI Language: %s" % self.mainConf.guiLang)
+        logger.info("GUI Language: %s", self.mainConf.guiLang)
 
         # Core Classes
         # ============
@@ -680,7 +680,7 @@ class GuiMain(QMainWindow):
         # Make sure main tab is in Editor view
         self.mainTabs.setCurrentWidget(self.splitDocs)
 
-        logger.debug("Viewing document with handle %s" % tHandle)
+        logger.debug("Viewing document with handle '%s'", tHandle)
         if self.docViewer.loadText(tHandle):
             if not self.splitView.isVisible():
                 bPos = self.splitMain.sizes()
@@ -805,13 +805,13 @@ class GuiMain(QMainWindow):
             logger.warning("No item selected")
             return False
 
-        logger.verbose("Opening item %s" % tHandle)
+        logger.verbose("Opening item '%s'", tHandle)
         nwItem = self.theProject.projTree[tHandle]
         if nwItem.itemType == nwItemType.FILE:
-            logger.verbose("Requested item %s is a file" % tHandle)
+            logger.verbose("Requested item '%s' is a file", tHandle)
             self.openDocument(tHandle, doScroll=False)
         else:
-            logger.verbose("Requested item %s is not a file" % tHandle)
+            logger.verbose("Requested item '%s' is not a file", tHandle)
 
         return True
 
@@ -838,7 +838,7 @@ class GuiMain(QMainWindow):
         if tItem.itemType not in nwLists.REG_TYPES:
             return
 
-        logger.verbose("Requesting change to item %s" % tHandle)
+        logger.verbose("Requesting change to item '%s'", tHandle)
         dlgProj = GuiItemEditor(self, tHandle)
         dlgProj.exec_()
         if dlgProj.result() == QDialog.Accepted:
@@ -888,7 +888,7 @@ class GuiMain(QMainWindow):
                 self.setStatus(self.tr("Indexing: '{0}'").format(self.tr("Unknown item")))
 
             if tItem is not None and tItem.itemType == nwItemType.FILE:
-                logger.verbose("Scanning: %s" % tItem.itemName)
+                logger.verbose("Scanning '%s'", tItem.itemName)
                 self.theIndex.reIndexHandle(tItem.itemHandle)
 
                 # Get Word Counts
@@ -1513,15 +1513,15 @@ class GuiMain(QMainWindow):
         we open it. Otherwise, we do nothing.
         """
         tHandle = tItem.data(self.treeView.C_NAME, Qt.UserRole)
-        logger.verbose("User double clicked tree item with handle %s" % tHandle)
+        logger.verbose("User double clicked tree item with handle '%s'", tHandle)
 
         nwItem = self.theProject.projTree[tHandle]
         if nwItem is not None:
             if nwItem.itemType == nwItemType.FILE:
-                logger.verbose("Requested item %s is a file" % tHandle)
+                logger.verbose("Requested item '%s' is a file", tHandle)
                 self.openDocument(tHandle, changeFocus=False, doScroll=False)
             else:
-                logger.verbose("Requested item %s is a folder" % tHandle)
+                logger.verbose("Requested item '%s' is a folder", tHandle)
 
         return
 
@@ -1545,15 +1545,15 @@ class GuiMain(QMainWindow):
         not change focus to the editor as double click does.
         """
         tHandle = self.treeView.getSelectedHandle()
-        logger.verbose("User pressed return on tree item with handle %s" % tHandle)
+        logger.verbose("User pressed return on tree item with handle '%s'", tHandle)
 
         nwItem = self.theProject.projTree[tHandle]
         if nwItem is not None:
             if nwItem.itemType == nwItemType.FILE:
-                logger.verbose("Requested item %s is a file" % tHandle)
+                logger.verbose("Requested item '%s' is a file", tHandle)
                 self.openDocument(tHandle, changeFocus=False, doScroll=False)
             else:
-                logger.verbose("Requested item %s is a folder" % tHandle)
+                logger.verbose("Requested item '%s' is a folder", tHandle)
 
         return