When I create a Tag or Link Property, I should be able to create the Model right there

(User Story, Closed -> Fixed, Priority: Critical, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Tag Sets, Properties, Editor
Summary: Experience has demonstrated that one of the most annoying workflow bugs is that I have to first create the Model, then create the Tag/Link Property pointing to it. This needs to be unified.
We probably need some special-case code in the Create Property panel; if you are creating a Tag or Link Property, you must explicitly choose one of "point to an existing Model", "create a new Model" or "let this point to anything", with "create a new Model" first, since it is the usual case. If you select that, it should offer you the Model's name, but allow you to change it.