Enabling of multi-tiered folders within personal galleries

Currently, the 'collection' feature for personal galleries only allows for a single folder, with no way to couple or tier for 'folders within folders'. I think a rename to 'folders' would be better, as well as expanding what folders can do in the form of multi-tiered folders.

My personal use for this feature would be to sort my art by type, and also year. While I acknowledge that tagging the artwork with the details would suffice, I would still like to be able to personally group my art in this manner. As such, the ability to post art into multiple groups/folders would also be needed, if not already implemented. (If this idea is not preferable, an input field for year made, in the case of older submissions, would be appreciated.)

I can see this feature being useful for groupings of photos from conventions, and character art collections.