Hm, something is strange. Possibly there is a permission not set correctly, but I cannot find it.
In my attempt to create a sub-gallery (image type), I created it in the list of parent galleries, not as a sub-gallery. I found that I cannot delete an image gallery, not even as admin ?! The gallery action "delete" is there, along with the red crossing icon, but it just doesn't do anything, also isn't written in blue hyperlink color. I checked the rights for image galley administration, and tried to add the right to set permissions to my user account, both did not succeed. As user or as admin, I cannot delete this image gallery.
I would prefer image galleries over file galleries, because file galleries do not show thumbnails...
Thanks for your support