I got what you meant.
And addendum to my previous post: FTR, to the connoisseur, nested tags is definitely not what calibre or Calibre Companion does. Although you can mimic it by creating multiple.hierarchical.tags with each dependency chain you want, you cannot actually put one tag inside another, and then change both tag chains with one edit.
(Considering that you always see all tags with calibre, that isn't so much of a problem... not sure how that works in CC which I don't use.)