Wanted to send a quick update...I now have 14 bit NRPN toggle buttons working! Got a great helping hand from someone on the Prophet12 forum who suggested I use the "val" keyword in my custom output button code. For NRPN code 11, I'm now sending:
$B0 $63 $00 $62 $0B $00 $26 val
and by setting the Custom output tab "Toggle" option and setting the "Value 1" knob to 0 and "Value 2" to 1, the button now sends alternate on and off messages to the NRPN code.
True 14 bit NRPN buttons! Hurray!