Hi brusch
The MOD has it’s own system and hardware for extra footswitches and expression pedals, it is reported the footswitches are in production but neither is available yet:
See here: Expression pedal + footswitch extender
I am also eagerly awaiting both items, in the meantime for playing at shows I have made a bunch of mini-pedalboards which can utilize the 2 footswitches on the MOD itself, Depending on how complicated your needs are this might be feasible. For now I simply scroll though the pedalboards with the left knob and click and load them for whatever the song requires.