On POD X3L, physical expression pedal positions, when assigned to a TWEAK parameter, will not be stored upon saving the patch.
However, the position or value of the effect parameters in Edit Mode (UI) that the TWEAK Pedal is assigned to, will be stored upon save.
This means that when you recall a patch with your expression pedal in the heel position, assuming the expression pedal is set to control a tweak parameter (IE: delay mix), the patch will recall the value you saved the tweak at (IE:Delay Mix 80%) and not the PHYSICAL PEDAL POSITION of the expression pedal (IE: Heel position or NO DELAY MIX)
This behavior is similar to the way the POD XTL and Vetta works.