The expression pedal can function in Classic Mode or Advanced Mode.
In Classic Mode, you can assign one parameter to each expressional pedal (A and B). Using the toe switch will select the other expression pedal and deactivate (bypass) the current expression pedal’s parameter. For example, if you assign a wah pedal to Expression Pedal A and a volume pedal to Expression Pedal B, only one of them will be active at any time; when you are controlling the wah pedal, the volume pedal will be bypassed, and vice versa.
In Advanced Mode, you can assign up to four parameters to each expression pedal (A and B). Moving the pedal will adjust all of its assigned parameters simultaneously. Using the toe switch will select the other expression pedal and leave the current pedal’s parameters active and at their maximum values.