Changing a Windowclass script in a FG3 extension

[Griogre]

I'm almost positive I read somewhere you can change a windowclass script in an FG3 extension without having to import the whole windowclass. Can someone point me to the reference on how to do this?

[Moon Wizard]

Define the windowclass again with the merge="join" attribute. Then, specify a new script tag/file. The script tag/file will be layered like templates behave with controls.

Cheers,
JPG