On the privileges page for creating tags it says:
When should I create new tags?
Most common tags already exist on a mature site. You should always favor existing tags; only create new tags when you feel you can make a strong case that your question does cover a new topic that nobody else has asked about before on this site.
But this doesn't seem to answer my question. It's unclear if a tag should only be created when there are no other tags that appropriately apply to the question, or if it's okay to do so whenever you personally feel that a topic isn't adequately covered by existing tag options.
For example, suppose you had a question about the Bekenstein bound. It would be appropriate to use tags like "black-holes", "black-hole-thermodynamics", "event-horizon", "gravity", and "general-relativity", but there is no existing tag for "Bekenstein-bound". Yes, that's within the realm of topics enveloped by those other tags, but none of them specifically address that concept.
Or alternatively, suppose you had a question about the complementarity paradox. Appropraite tags include things like "hawking-radiation", "entanglement", and possibly "black-hole-firewall", but there exist no tags for "complementarity-paradox", "fuzzballs", or "ER=EPR". So should such tags be created, or should you just rely on the existing ones since they are inherently connected topics?
I'm not trying to push any buttons or start any arguments. I'm just seeking further clarity on when this privilege should be used.