Great news...I got if figured out...well, mostly. I've been able to use the MountainUtilities editor to send the proper custom output sysex to turn the P12 parameter for NRPN 11 on and off from a button.
On: $B0 $63 $00 $62 $0B $06 $00 $26 $01
Off: $B0 $63 $00 $62 $0B $06 $00 $26 $00
Now I'm wondering if the button toggle feature is available in the custom output mode? I've been able to turn the parameter on OR off from a single button but not toggle through both on AND off states with a single button. I've tried all possible combinations in the editor but can't get the buttons to toggle between 2 unique sysex strings...is this possible?
Thanks!