Faced with the same situation, I discovered a work-around. When you import the GPX as favourites, the new POIs go into the default folder called "Favourites". If you make sure that prior to the import this folder is empty (or even deleted) by moving any contents to other named folders, then after the import your new POIs are all in the "Favourites" folder by them selves. Then you can simply rename "Favourites" to whatever you like, change its appearance, etc.
You can do this repeatedly - if you made a second import, OsmAnd would recreate "Favourites" for the new POIs, and you can rename it again.
It's an easy system once you get into the habit of using "Favourites" solely for importing.
I hope that helps! I think I made it sound more complicated than it is...