I think that @Tweaker’s question is less about MIDI handling inside Cantabile, rather about the behavior of the XP-80.
Am I correct in assuming that you want to use the bank/program buttons of the XP-80 (the ones underneath the display) to operate things in Cantabile?
As far as I can recall (I used to own an XP-80 years ago), selecting a different bank on the XP-80 automatically also loads a program in that bank (the one corresponding to the currently selected “program” button). So pressing a bank button will always also result in a program change being executed - I don’t believe there is a way around that. It’s just the way the XP-80 operates.
These buttons are just not primarily designed as “master keyboard controls”; rather they are designed to quickly select patches in the classic Roland 8x8 method. There is no system setting that will make them behave differently, AFAIK.
Guess you’ll need to work within the constraints of this system, I’m afraid…