To assign specific tones to your MK2 Express pedals:
1.Select a desired tone from the app - either one of your saved tones or one of theirs. Play it to make sure it's correct.
2. Exit the App on your device (iPad, phone). For some reason It will not work with the app open. Your selected tone should still be there even after closing the app.
3. If your tone is still there (it should be), press and hold the Tone button on the amp until the preset lights start flashing (should take about 3-4 seconds).
4. Once flashing, release the Tone button and then tap the Tone button to scroll thru the presets (a,b,c or d) until you get to the place you want to assign the selected tone.
5. Now press and hold the Tone button for about 2 seconds. Your tone should be assigned to the pedal that you selected.
After much trial and error this just worked for me so i figured i'd share. Pick the 4 tones you'd play most bc as far as i can tell, the pedal only works for 4 - you cannot switch banks using the pedal - or even the amp. It seems you can only do that using the app.