The idea was to use two 20k potentiometers on the shaft of the stepper. When poti is in its dead zone, the other poti could be used.

The hole in the middle hat to be squared a bit to fit onto the shaft by using a solding iron.

First I 3D rinted a small distance pice.To mount the two potentiometers, I had to get a holder with higher side walls and a small seperator for the potentiometers. The spring contacts, I grinded very flat and mounted by 180 degree rotated to each other.Flipping the second potentiomater to the top would give me the dual potentiometger stepper I was looking for. The remaining shaft on the top was kind of small and there was a mechanism missing to push the both potentiometers and the coils inside together. Also the printing tollerances had not been good and it was a bit wobbling.