Hiding parent folder hides all subfolders

I have a macbook, and an external hard drive for my photos in lightroom (6.8)

My folder structure looks like this in Lightroom:

Folders:

Macintosh HD 3/120GB

--> /

------> Volumes

---------->Buffalo

---------------> (a set of subfolders)

--------------------> (all subfolders by year, which include my photos)

Now, I want to shorten this whole folder structure so that all that I see is the "all subfolders by year", because no of the other parents have any pictures in them.

Right-clicking the "/" folder allows me to hide this parent, and all works fine. However, right-clicking "Volumes" and pressing "Hide this parent" results in all subfolders being removed from the folder structure (though no photos or subfolders are "deleted", they're simply not viewed. I can reverse the action by clicking command z). After this, the whole folder selection in the left bar is empty.

Right clicking "Buffalo" or any of the "set of subfolders" does not show any alternative to hide the parent folders.

How should I go about to only be able to see my subfolders by year?

Thank you