Does that override existing expression pedal assignments though?
No. If used on a per preset basis, you can also use other expression pedal assignments.
I would like to add output level changes to other parameter changes, for example: in Crushstation have the expression pedal control gain from 15-30 and output volume from 0dB to +6dB at the same time.Show More...
Oh, well that it doesn't do. It doesn't give you an assignable range of output volume. It goes from silence to full output volume over the range of the expression pedal.