If voltage from pedal is added to voltage from the knob in hardware, what you ask may not be possible.
But, even if it was possible to modify this in firmware, how would it work if you also have an LFO or envelope affecting cutoff? If knob is at 20% and LFO is at 25%, so total cutoff is at 45%, then when full travel of pedal would have a range of the other 55% of cutoff. But, a moment later LFO would be at -10%, for a total of 10% cutoff, so what would be the range of the pedal, 90%? Or would you just ignore the LFO and keep it at 80% if knob is at 20%? Either way, I think it is exactly fine as it is.