Following some discussion, we've decided to implement a new category: subclusters.
Subclusters are parts of the Backrooms that share a unique property with each other, or that are self-contained, meaning that they are distinct from the rest of the Backrooms.
It all starts with levels, but subclusters can also contain their own unique entities, groups, phenomena, objects, and more!
The pages that fit this description, and that meet the requirement of having 3 or more associated pages with the subcluster, are permitted to create a hub page for the subcluster, and add the tag "subcluster" to its associated pages.
Subclusters can be found on the hub below, which is the same place where series are found; they follow the same format.
https://backrooms-wiki.wikidot.com/series-and-subclusters-hub