Is the 4th extruder in marlin yet? There is a MaukCC branch on github where 4 nozzle temps are in, but no 4th extruder. Maybe usefull, not having to start from scratch. Also for multiple extruders it is very helpfull to have a graphic display, to see the nozzle temp state in one glance. This is also for 3 nozzles at the time. I would suggest moving the heated bed, fan, and eventually the chamber temp to a lower line in the display.