Thanks Daniel for your interest.

As usual, I have a strange "do-it-yoursef" approach to this kind of difficult topics. So I can't guess if/where/how this kind of topic has been discussed (I saw lots of discussions on categorization, many of them so much exoteric than I can't undestand them; nor I'm interested into extensions development, I have much fun using existing, basic tools) . Nevertheless, in my tryes, such e trick turned out very simple to use, you can add and remove "axes", "branches" and "leaves" and to convert a "leaf" (i.e. a "terminal category") into a "branch"... a couple of more interested comments, and I'll implement just some of such "catwords" into Commons, just to let you see how they precisely work.