Photo Album Confusion

When I try to create a new album, I’d like to pick specific folders within a library. However it adds every single photo in the library, regardless of what photo they are within.

I see that it’s possible to cherry pick individual photos but not folders or groups of photos.

Am I correct? If not, someone please help.
I’d really appreciate it.

My photos are organized in folders by Year, then Subject, so the folder structure is like this:

photos
-----2016
------------subject 1
------------subject 2
------------subject 3

In Plex, using Photos view, it looks like this:

If you select ‘Add to Album’ from a Folder’s overflow menu, it should add only the photos in that folder to the Album.