I've already read the handbook and experimented myself.
You can send midi when in ABCD mode as each patch, when switched to will send a pgm change.so 1A will send PGM001, 1B will send PGM002 etc. This can not be altered.
If your amp has midi and a midi learn function, you can teach it what the midi PGM is for each patch and in turn control amp channels.
I had a Bugera TRIREC but its gone now.