diff --git a/app/src/processing/app/Mode.java b/app/src/processing/app/Mode.java
index 86db49269..31b82fc56 100644
--- a/app/src/processing/app/Mode.java
+++ b/app/src/processing/app/Mode.java
@@ -345,11 +345,11 @@ public abstract class Mode {
   public void rebuildLibraryList() {
     //new Exception("Rebuilding library list").printStackTrace(System.out);
     // reset the table mapping imports to libraries
-    HashMap<String, List<Library>> importToLibraryTable = new HashMap<>();
+    Map<String, List<Library>> newTable = new HashMap<>();
 
     Library core = getCoreLibrary();
     if (core != null) {
-      core.addPackageList(importToLibraryTable);
+      core.addPackageList(newTable);
     }
 
     coreLibraries = Library.list(librariesFolder);
@@ -367,28 +367,16 @@ public abstract class Mode {
     coreLibraries.addAll(foundationLibraries);
     contribLibraries.removeAll(foundationLibraries);
 
-    /*
-    File sketchbookLibs = Base.getSketchbookLibrariesFolder();
-    File videoFolder = new File(sketchbookLibs, "video");
-    if (videoFolder.exists()) {
-      coreLibraries.add(new Library(videoFolder));
-    }
-    File soundFolder = new File(sketchbookLibs, "sound");
-    if (soundFolder.exists()) {
-      coreLibraries.add(new Library(soundFolder));
-    }
-    */
-
     for (Library lib : coreLibraries) {
-      lib.addPackageList(importToLibraryTable);
+      lib.addPackageList(newTable);
     }
 
     for (Library lib : contribLibraries) {
-      lib.addPackageList(importToLibraryTable);
+      lib.addPackageList(newTable);
     }
 
     // Make this Map thread-safe
-    this.importToLibraryTable = Collections.unmodifiableMap(importToLibraryTable);
+    importToLibraryTable = Collections.unmodifiableMap(newTable);
 
     if (base != null) {
       base.getEditors().forEach(Editor::librariesChanged);
@@ -630,6 +618,18 @@ public abstract class Mode {
   }
 
 
+  /**
+   * Require examples to explicitly state that they're compatible with this
+   * Mode before they're included. Helpful for Modes like p5js or Python
+   * where the .java examples cannot be used.
+   * @since 3.2
+   * @return true if an examples package must list this Mode's identifier
+   */
+  public boolean requireExampleCompatibility() {
+    return false;
+  }
+
+
   /**
    * Override this to control the order of the first set of example folders
    * and how they appear in the examples window.
diff --git a/app/src/processing/app/contrib/ExamplesContribution.java b/app/src/processing/app/contrib/ExamplesContribution.java
index be4782e4b..c922eea9a 100644
--- a/app/src/processing/app/contrib/ExamplesContribution.java
+++ b/app/src/processing/app/contrib/ExamplesContribution.java
@@ -6,6 +6,7 @@ import java.util.List;
 import java.util.Map;
 
 import processing.app.Base;
+import processing.app.Mode;
 import processing.core.PApplet;
 import processing.data.StringDict;
 import processing.data.StringList;
@@ -57,11 +58,16 @@ public class ExamplesContribution extends LocalContribution {
    *         active editor
    */
   static public boolean isCompatible(Base base, StringDict props) {
-    String currentIdentifier =
-      base.getActiveEditor().getMode().getIdentifier();
+    Mode mode = base.getActiveEditor().getMode();
+    String currentIdentifier = mode.getIdentifier();
     StringList compatibleList = parseModeList(props);
     if (compatibleList.size() == 0) {
-      return true;  // if no mode specified, assume compatible everywhere
+      if (mode.requireExampleCompatibility()) {
+        // for p5js (and maybe Python), examples must specify that they work
+        return false;
+      }
+      // if no Mode specified, assume compatible everywhere
+      return true;
     }
     for (String c : compatibleList) {
       if (c.equals(currentIdentifier)) {
diff --git a/app/src/processing/app/ui/ExamplesFrame.java b/app/src/processing/app/ui/ExamplesFrame.java
index de13a4c24..105858a87 100644
--- a/app/src/processing/app/ui/ExamplesFrame.java
+++ b/app/src/processing/app/ui/ExamplesFrame.java
@@ -342,8 +342,7 @@ public class ExamplesFrame extends JFrame {
       e.printStackTrace();
     }
 
-    DefaultMutableTreeNode contributedExamplesNode =
-      buildContribTree();
+    DefaultMutableTreeNode contributedExamplesNode = buildContribTree();
     if (contributedExamplesNode.getChildCount() > 0) {
       root.add(contributedExamplesNode);
     }
diff --git a/todo.txt b/todo.txt
index 652544458..667f90556 100755
--- a/todo.txt
+++ b/todo.txt
@@ -20,6 +20,9 @@ o saying "no" to save changes is the same as "cancel" on windows?
 X   can't reproduce
 X add printStackTrace() method that can be overridden
 X   https://github.com/processing/processing/issues/222
+X write preferences.txt using a temporary file
+X   also save the previous version as preferences.old
+X   https://github.com/processing/processing/issues/4614
 _ update launch4j to 3.9
 _   https://sourceforge.net/projects/launch4j/files/launch4j-3/3.9/
 
@@ -41,6 +44,7 @@ X implement templates
 _   write short docs
 _   https://github.com/processing/processing/issues/4306
 _   https://github.com/processing/processing/issues/4352
+X add Mode.requireExampleCompatibility()
 
 contrib
 X use HTML to print