Russell Croman's StarXTerminator plugin is incredibly useful for astrophotography post-production. In this video, I'll show you how to use it to create a separate star layer which can then be composited over the top of your retouching on the starless data.
If you want to try the astrophotography macros for Affinity Photo, they're a free download from my website: https://jamesritson.co.uk/resources