You can do following:
1. a single momentary switch for one function
2. two momentary switches with a Y-split cord (TRS-jack into two mono jacks) or
3. build a custom pedal with three momentary switches according to the attached drawing below.
The used switch type must be momentary (door-bell / pulse /sustain) types (like the BOSS FS-5U or the PROEL PFS24).