Because changing nozzles with the supplied multi-tool was too wobbly for me, I developed a simple tool to hold the hotend more stable.
As can be seen in the CAD image in cross-section, the tool is designed in such a way that the hotend reaches the stop at the back and cannot slip through. This prevents it from moving during the tightening process.
I printed the tool out of PETG with 100% infill and a layer thickness of 0.2mm. With the correct orientation, no support structures are necessary.
Update 01.11.2023:
Since some users are not so satisfied with the tight fit, I have added a version with higher tolerances and loose fit (file with addition "loose_fit")
The author marked this model as their own original creation.