From T186591:

• Since categories cannot be added right now there should be a another free text field where plain wikitext can be entered. This should then be appended to the end of the description page. It could simply be called something like ("Categories, as wikitext"). If empty then add [[Category:3D models]] (?)
• The description field should be re-labelled description rather than description page as it now only accepts the information which goes into the description field of the information template (whereas before it accepted the whole page). Ideally it should also be clarified that this should be plain text (not wikitext) as the same field is re-used for Sketchfab.
  • The same applies to the label on the preview page.

Allowing categories (and the Sketchfab equivalent) to be set in a more dynamic way (using the api to auto-complete suggestions).