You can't directly. CC 110 (decimal) is out of range for Montage. You can only set controllers up to CC 95. CC 110 is just an on/off switch for harmony - so you don't really need anything more than a button or footswitch for that. But because you cannot assign higher than 95 - will CC 12 work - which is Harmony Level? Can you set harmony level to 0 as another way to turn off harmony (CC12=0).

FYI - you can use superknob to send CC12 if you wanted to.

And set superknob CC to 12. However, that's overkill since superknob will transmit continuous values between 0 and 127. There are the two buttons for "jumping" between two preset values of superknob you can use. But still, it locks you out of using superknob for other purposes which may not be what you want.

You could also use the footswitch - purchase latched switch (or one that can be switched between momentary and latched - I think Roland makes one) and then modify "FS Assign" (same screen shown above) to set the CC to 12. This will give CC 12 = 0 and CC 12 = 127 depending on if the pedal is latched or not (clicked on vs. clicked off). This all depends on CC 12 doing the "same" thing as CC 110 "at the end of the day". The problem with level and the footswitch is that you may not want the "on" level to be 127. That may or may not be something you can somehow compensate with other settings of the pedal. I'm not reading the entire manual to determine all those details.

If you'd rather not use footswitch or superknob, then go to this menu:

And set the CC of any of these controllers (Ribbon, FC1/FC2, Assignable SW1/2, etc .. etc..) The switches are going to give you problems with being able to "dial in" the level you want if 127 doesn't work for you. Continuous controllers (with more than on and off) are going to present issues in achieving the value you want. I'd have to take a look to see if assignable knobs transmit. Even if they do - for precision you're likely going to want to tie these to superknob to be able to control the "on" and "off" values with precision. It's almost the same as just using the superknob CC directly (although would give some incremental flexibility).

Thanks! You’ve been very helpful.