Entry folder

[xsus95]

I’m looking for a way to define the top folder for the gallery app

Concretely, my structure looks like this:
root-folder -> image-folder
root-folder -> image-folder -> image-folder 1
root-folder -> image-folder -> image-folder 2
root-folder -> documents-folder
root-folder -> xx-folder
root-folder -> xy-folder
root-folder -> xz-folder

In the gallery app the first folder that shows up is “gallery-folder”. Afterwards there are all subfolders.
I would like to ONLY see the subfolders (“image-folder 1”, etc), not the ones called “image-folder”.

.nomedia is not an option, as the subfolders will also be hidden then.