Increase the overlap of the mosaic job creator

Yes it is an unusal request. Please think differently: Much more overlap, so that the difference between dithering and mosaicing is blurred, 75% overlap! Expose partly on top of each other and partly next to each other, then it will also work with the windsorized sigma rejection. Remember, it needs 13 layers on top of each other to work. Most people don't understand that either and you won't find it anywhere. You learn it by trial and error. This is done with 75% overlay (=4 layers) and 4 passes, i.e. 13-16 layers in the core area.

A side aspect is to be able to choose the Mosaic FOV more to your needs.

Please give it a try in Kstars and allow an overlap of 75%. This creates better mosaics where you don't see the overlapping areas.