The current MMVP approach in Cite implemented in https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cite/+/1040265 still needs to support to give autonames whenever a reference is saved and extended that did not have a name yet. Follow the same internal pattern as is used for reuse, eg. use the "list key" which looks like "auto/#" until the "literal/:0" automatic name has been assigned during save.
Use the the same ":0", ":1"... naming pattern as already exists for normal ref reuse.
The patch currently already ensures that autonames are saved whenever a reference is used as parent. Just the numbering of the autonames does not seem to match at the moment and needs so more work it seems.
Should be possible to include a QUnit test—especially if it helps to follow TDD as we write the feature.