Looping part of a multitrack song for playing with the audience

There’s different ways to have markers.

1. You can insert markers to the song during recording by push the skip back skip forward key. That’s not relevant for your setup.
2. Uses markers and loop on the fly where you have no markers in the song but you want to set up the loop. This is the thing what you described. But that’s not enough good for live performance as the markers are inaccurate because you set up on the fly.
3. Include the markers in the song: This can be done really precisely as you need to define the markers in uTool. This is the way how you should do it for your use case.

You also need to know the loop function will loop all the song not just several tracks like the clicktrack.
In your case you need to have a marker at the beginning of the song and one in the “middle”
“With your solution, we can only play the part in between the markers or am I missing something.”
With this until the loop exist it will loop the part between the markers and when you remove the loop the playback will continue (no matter where was the marker) and plays out the whole song.
That’s true you cannot do that with footswitch but you can use uRemote to remote control the device, so the uTrack24 can be anywhere.