When submitting a file the created extension gets a user right away.
This makes sure there are no orphans extensions.
The extension is then incomplete until the draft is saved once (which
means finalizing the extension upload process, by adding a description
and thumbnails).
Any attempt to edit or submit a new extension will lead the user to the
editing draft page.
Note: We could add a new option to [x] Send for Review. The front-end
even has a half-baked code for that. But should be tackled separately.
