Fred's correct. All foot pedal assignments are memorized on a "registration by registration" basis. If you have a bunch of songs where you need the app/harmony assigned in that fashion, create a registration template called App/Harmony Blank, or something similar. To create a new registration, use the template registration, and then rename it in the Save function.
I often use my sustain pedal to pitch bend the Pedal Steel effect. I save that to Button 1, and then Button 2 may be set to sustain for the piano voice. Registrations give us huge control over our instrument.