I assume this is a generic Ubuntu issue, not specifically Budgie. If I need to take it elsewhere, let me know.
I have a png file that is used by an app and held in a dot directory in my home dir. I installed the snap version of Gimp, 2.10.20, from the store so that I could edit that image. I quickly discovered that Gimp would not open it due to permissions, even though they are fine all along the path. I have set the permissions in the snap store so that Gimp can open detachable drives, even though this is in my user dir. I was never able to make it work. I finally uninstalled the snap version and installed v2.10.18 via apt. This form of the app opens and saves that file fine.
Any idea why the snap version couldn’t open a file in a hidden directory?