MIDI Designer introduces Channel Changers in version 1.3.
Make a multifunction control by using more than one MIDI channel. One knob controls the channel for its subcontrols.
“Knob Q” controls “Wah Filter” on Channel 1, CC 42 and “Delay Feedback” on Channel 2, CC 42. “ChChger” is the supercontrol that makes Knob Q switch between functions. Knob Q will snap to its last value for “Wah Filter” and “Delay Feedback” when you switch the channel.
Set It Up
Make a knob, slider, or cross-fader a “channel changer.” Now it’s a supercontrol. Add some subcontrols and that’s it. Automatic and easy.
Check this Q&A answer for detailed instructions (on iPhone, but they’re the same).
Change the value on the knob to change the channel on the subcontrols. They snap to their previous value when they were last on that channel.
This works for sysex (0-127) as of MIDI Designer 1.5.0 (Released April 15, 2013), too.