Welcome!
I think you can use “Global Midi” Settings to advance forward or back between the 4 rackspaces/songs using 2 pedals on your foot controller. You could use the other two pedals to move between variations/song parts.
With only 4 rackspaces, this may work perfectly fine for you. (You should be able to get to any of the 4 rackspaces pretty quickly)
However, if you want to be able to select among the 4 pedals (e.g., go from rackspace 1 to rackspace 3), then a different technique is required.
As I understand it, you would usually use PC messages for this.
I think there may be ways (within GP?) to convert CC messages to PC messages to select specific rackspaces. Others, with more knowledge than me, may able to give you more guidance.
Jeff
PS: I found these discussions that may be helpful: