Supreme Directory Overrides

What’s the best way to make modifications to Supreme Directory so that updates don’t wipe out my changes? I like Supreme Directory so I would rather not use it as a model and build another. Especially since needed updates for it come out often. It gets updated like it’s a parent theme. Is there a way to make a child theme, of a child theme? Or is there some sort of overrides system I’m not aware of? Somebody had to have thought of this at some point.

Wil