re: Cable Entry/Exit (a work in progress)

I like your split panel idea, but it probably is overkill. Still, as you mentioned, it will keep things tidy. It’s also one of those nice touches that will make the cabinet uniquely yours, even though nobody but you will ever see it.

Your scallop idea seems sufficient. If you go that route, you could always use a strip of veneer to cover the exposed plies.