Sorry for the mess 🙈️ and thanks a lot for digging into the problem. Personally, I believe the only sustainable option (besides talking to each other 😅️) is to rely on test cases when we work on this code together, across teams and continents. Unfortunately it looks like neither of the two edge-cases you discovered was covered.

Is there anything left the WMDE-TechWish team can help with here?

We actually talked about this feature when the WMDE-TechWish team worked on the WMDE-Templates-FocusArea. Together with WMDE-Design we decided that it's not the best idea for the exact reasons @DLynch mentioned above. It's also exceptionally rare that someone would need this as an actual feature. I mean, what's the use case, other than an accidental mis-click? Why would someone remove a parameter just to add it back with the same value?

The behavior is also the same when I delete both refs. The result is that the artificial list-defined main reference is left behind with no usage anywhere.

<references>
<ref name="book">Miller 2025</ref>
</references>

This is pretty much the exact same situation as above, just that there is no other sub-ref left at the end. The main ref should be completely removed then.

Note the current behavior is the same for both these examples:

<ref name="book" details="page 1">Miller 2025</ref>
<ref name="book" details="page 2" />

<ref name="book" details="page 1">Miller 2025</ref>
<ref name="book" />

In both cases, when I delete the 1st ref the content currently doesn't move to the 2nd ref (expected behavior) but into the reflist (current behavior). This ticket will probably fix both cases.

it doesn't sound like there's any other data that we want to show.

Can you add some examples or links to examples in the task description? This sounds like it might be very relvant to the work the WMDE-TechWish team is currently doing in Sub-referencing. Unfortunately there is no information in the ticket other than the title.