I couldn’t get it to work via the H90 control, for whatever reason. It accepted the change at the pedal. Not sure why or what I did wrong. I plan on resetting at some point and attempting this process to assure I have it correct. Thanks so much for your help!!!!

Regardless, for those looking to use the Expression pedal to mimic a Wah Wah Pedal, here’s the process.

SP-H9 – TRS to dual TS cable, connect one end to EXP 1 for expression and the other to EXP 2 for aux switch(4).

In H90 Control, go to Control Assignments > Performance Parameter Mapping, select P switch > Parameter: Act/Byp > Control Source: Aux Switch #4. This will make the switch act/bypass the Program. Make sure you save the Program when you are done.

You can also go to System > External Control and map this globally so the aux switch does act/bypass for every Program.