I use parts of
Geralds video tutorials for enhancing nebulosity in pixinsight. His process basically reduces bright stars down to smaller and its a process you can run a couple of times to remove all the stars, so nebulosity can be brought out then the stars put back later. But following the tutorial I find often the star reduction process gives me sharper rounder more colour looking stars. For you PixInsight I can't recommend Geralds videos enough and for everyone else give them a watch and you might find the same sort of tools in your package of choice. He has some great approaches to universal problems and I never would have thought of using some of the tools in PixInsight for other purposes.