I like this plugin, but my project already has a class named ContextMenu, so I had to modify QuickSettings before it would load correctly.
There’s no real reason for ContextMenu or RenamePropertyDialog to have class_name defined, since you only ever create a single instance of each.
edit: This also applies to ArrayEditor and VectorEditor, since ArrayEditor only has a single instance, and for VectorEditor you preload the scene.