So you might be talking about the LEARN function.. which I don’t use.. but I think it is an Aux switch function. You push it, and it flips the ROOT of the key to whatever you are playing right then. I will try it next time I think of it.. but I don’t remember it being that reliable ON GUITAR. It may well be better with keys…. and I am unclear if I can change MODES (maj–>minor) or just Root Notes.
Now..although you said you didnt want to..using different patches really would be the most elegant way if your changes are pre-planned
. You can just use a single button by pre-planning your patch changes and laying them in a row. No need to go back down… you just duplicate your patches in one direction. So one touch, and you are in a different, previously designated key/mode. . . just like you want.
Of course.. if duplicate patches offends ones OCD… with a MIDI pedal like a Disaster area DMC, you would have one-touch patch changes up AND down, leaving your Aux switch free for the Performance Switch function. And the performance switch IS awesome.. so it may be worth it. And the switching is really seamless if you don’t change pre/post function.