@drvo, I agree with you that having the ability to add custom FITS fields would be nice, for the same reason you mentioned in the other post.
I’m aware of Pixinsight’s ability to group by directory/filename, but I’m trying to avoid that since the names get unwieldy when you add FLAT_YYYYMMDD, BIAS_YYYYMMDD, and DARK_YYYYMMDD. That also means in many cases I’ll need to manually separate images in a target.