Remove ability to delete content and source folders. Limit CM options on those folders only to ones that make sense.

Source/Editor/Content/Tree/ContentTreeNode.cs

@@ -24,6 +24,11 @@ namespace FlaxEditor.Content
         /// </summary>
         protected ContentFolder _folder;
 
+        /// <summary>
+        /// Whether this node can be deleted.
+        /// </summary>
+        protected virtual bool _canDelete => true;
+
         /// <summary>
         /// Gets the content folder item.
         /// </summary>
@@ -301,7 +306,7 @@ namespace FlaxEditor.Content
                     StartRenaming();
                     return true;
                 case KeyboardKeys.Delete:
-                    if (Folder.Exists)
+                    if (Folder.Exists && _canDelete)
                         Editor.Instance.Windows.ContentWin.Delete(Folder);
                     return true;
                 }

Source/Editor/Content/Tree/MainContentTreeNode.cs

@@ -12,6 +12,9 @@ namespace FlaxEditor.Content
     {
         private FileSystemWatcher _watcher;
 
+        /// <inheritdoc />
+        protected override bool _canDelete => false;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="MainContentTreeNode"/> class.
         /// </summary>

Source/Editor/Windows/ContentWindow.ContextMenu.cs

@@ -114,18 +114,28 @@ namespace FlaxEditor.Windows
                     }
                 }
 
-                cm.AddButton("Delete", () => Delete(item));
+                if (isFolder && folder.Node is not MainContentTreeNode)
+                {
+                    cm.AddButton("Delete", () => Delete(item));
 
-                cm.AddSeparator();
+                    cm.AddSeparator();
 
-                cm.AddButton("Duplicate", _view.Duplicate);
+                    cm.AddButton("Duplicate", _view.Duplicate);
 
-                cm.AddButton("Copy", _view.Copy);
+                    cm.AddButton("Copy", _view.Copy);
+                }
+                else
+                {
+                    cm.AddSeparator();
+                }
 
                 b = cm.AddButton("Paste", _view.Paste);
                 b.Enabled = _view.CanPaste();
 
-                cm.AddButton("Rename", () => Rename(item));
+                if (isFolder && folder.Node is not MainContentTreeNode)
+                {
+                    cm.AddButton("Rename", () => Rename(item));
+                }
 
                 // Custom options
                 ContextMenuShow?.Invoke(cm, item);