One of my frustrations with the MMU2 experience is that I was never looking at it when an event occured that caused a load error, unload error, skipped layer etc. In addition I wanted a way to quickly assess the effect of Slic3r settings on stringing, tip shape, etc.
I created a 100mm tall square object that changes color (tool change) every millimeter and incorporates all five colors (tools). It is obviously based on the 20mm calibration cube. The sequencing of the tool changes varies from top to bottom. You can change the sequencing by selecting the object in the 3D view which brings up the Settings window. Select any of the objects labelled 'lambda-slab' and change the extruder number. You can change any of the other Slic3r settings as you normally do.
The object needs a Brim in my experience. Otherwise you run the risk of the extruder knocking it over.
Object produced in Tinkercad.