"MMU Bowden Bypass" for temporary frustration relief
Having experienced the frustration of going from a very reliable stock Prusa i3 MK2S to the more challenging MMU upgrade, I came up with this idea for a temporary retrograde to a single extrusion system that can easily be reconverted to MMU when you are up for it. The basic idea is to remove the Y Splitter and the short PTFE tube in the hot end and replace it with a piece of standard 4mm OD 2mm ID PTFE tubing. Unfortunatley, I don't think the stock Bowden tubes are quite long enough to simply reuse one of them.
This Bowden Bypass has the advantage of removing the complexity of the Y Splitter for simple single extrusion, high quality printing. You still get to use the Bondtech geared extruder (a very good thing) and since the extruder is not on the X carriage, the carriage is lighter. The short Bowden is not a significant issue in terms of print quality. Yet, when you want to take another shot at MM printing, you can quickly and easily go back.
Here is a drawing:
Note, I have not actually tested this myself. It was an idea I wanted to try but I sold my Prusa i3 MK2S with MMU and the new owner (who is new to 3D printing) asked if there was a way to revert back to the single extrusion system. I think this idea should work well. If you try it, please report back.
Once you've made this change, slice with the "Original Prusa i3 MK2 MM Single Mode" printer profile in Slic3r PE.