In our docs we had a structure:
  1. Category
1.A. Sub-category
1.A.x Sub-sub-category
And while I opened our knowledge base page for the Category I didn't see the Sub-category there. It only then appeared when I copied an article in it.
I guess before that it was seen as empty, although it had four Sub-sub-categories in it.
Would like to see the Categories and Sub-categories then too when there are no articles directly under them.