I'm not sure if you're trying to set "Digital Part Volume" - which is address 0x30 0x4F 0x01 (with value 0x00 - 0x7F, defaults at 0x64). If this is the one, then an external MIDI footswitch controller (which does SysEx) can map to this. Or possibly an audrino (or other DIY electronics) if you're up to that.

I do not see "USB" or "digital" in the controller box destinations - so there's no assigning this to superknob that I can tell.

Thanks Jason. I don't wanna buy other device. It is only a suggestion for better future firmware:--)

As is often the case - I provide suggestions based off of what can be done now even if the request requires a firmware change. This is to allow the end user to explore some alternatives while they wait - possibly forever - for a firmware update.

I wouldn't want to purchase or make my own hardware to lug around for this either. Incidentally - you could also use a laptop for this and possibly not purchase anything - but have to lug around something else. I'm anti-laptop here because I want my keyboard(s) to stand on their own. I'm allowed to have that configuration "rule" for myself -- personal preference. I also realize you have your own personal preference - which probably matches mine - and would preclude adding some extra stuff to lug around. Or you may just not want to pay any more for things that would be better left to Montage itself - I get that.

For the "lug around" side - I do not have foot controllers on gigs with me. But if you do lug around foot controllers -- you may be able to replace these with a MIDI foot controller and have a net unity in what you lug around.

A MIDI foot controller is not equivalent to a passive foot controller (like the FC7). There are combo foot controllers that do both passive and MIDI. Last I looked one of these was getting mothballed (meaning the company was going to stop making them).

This is one such beast: http://www.sourceaudio.net/reflex-expression-controller.html

Still not saying to do this - but if you ever give up on firmware and have some cash to spend -- it's an option.

Note that if you do "allow" a laptop or MIDI-connected tablet or otherwise some computer-type-thing - then you could also echo back a message and re-configure the message to target the SysEx (if that MIDI address I have hh mm ll works for you). The computer can take a CC or Sysex generated by a knob already on Montage (like assignable knobs or superknob) and re-package the message into the target sysex for digital volume. There are several options here - some free - some at cost. Bome is one, it'll cost (I'm not sure Bome classic lets you do this - which is free). Ctrlr is free - but requires, I believe for this task, to make a lua script. There are probably other options out there. Those were both windows-centric software suggestions. Mac has its own stuff. And maybe tablets and phones have something that will work using bluetooth MIDI - but requires a relatively cheap adapter purchase.

As always - this isn't what you "should" do - but what you "could" do. You make the final call.