Was playing around a bit this past week and playing with the fader for vintage/drift/madness during performance sounds really awesome to me.
Being able to set this as a modulation target would’ve been incredibly valuable. Is there a way this could happen? It’s of course not possible to just set it the normal way by holding mod source and changing the fader, since then I’m no longer in shift mode 
Anyway, it would be amazing to be able to control it with an expression pedal or envelopes maybe.
