Wah and Volume pedal - alter the Exp. pedal function, possible?

In system menu select wah to volume. When you have a wah active in a stomp the expression pedal becomes wah when there is no wah in the stomps the pedal becomes a volume

Follow Raoul's message. There is also a setting for pitch to wah so if you check both of them, the pedal can be pitch if you have a pitch effect turned on, or a wah if you have one enabled, and will default to volume if neither of the first two are in use.

very helpful feature.