I am wondering how much fiddling I would have to do during a performance to send a program change message from #1 port(DM48), as there are no keystrokes or GUI available, just a scrolling parameter window on the harmonica.

All of you have been great in trying to help me out, but, it seems that a module does not lend itself to simultaneous commands very easily. If this is the case, there are always workarounds.
1. Program registrations with a DM48 patch and have the other three for keyboard, which my new Microkey 61 is working fine.
2. Play over SMF files using "Favorite Instruments" folder.

I just feel guilty about taking your time if it isn't practical.