This is a solution I found to handle wha and volume with same pedal in a different scene
I use M-plex
Channel A - Row 2 (wha)
Channel B - Row 3 (Volume)
when you change the scene you can select M-Plex channel you want
in the third image I select off value for wha at 95%
In this way you can keep volume pedal at maximum, when you select sense with wha it start only if you push down the pedal.
With off value to zero you have problem when the volume is selected because it start from zero.
My English is bad but you should understand
I use M-plex
Channel A - Row 2 (wha)
Channel B - Row 3 (Volume)
when you change the scene you can select M-Plex channel you want
in the third image I select off value for wha at 95%
In this way you can keep volume pedal at maximum, when you select sense with wha it start only if you push down the pedal.
With off value to zero you have problem when the volume is selected because it start from zero.
My English is bad but you should understand