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The Editor window's 'Insert Code.../Add Property' at the moment does not check to see if class it is modifying extends a class which already has a PropertyChangeSupport field. If so, it would be useful to reuse this existing property support instead of creating a new one in the subclass.
This is a good idea. Implementation is however non-trivial, targeting next release.
Another thing you may want to do is make the generated PropertyChangeSupport protected instead of private.