@thiemowmde agreed that this is what is happening in wikitext/from the technical perspective, but from the user perspective in VisualEditor users are 'inserting' Details, not applying changes to the details. This was always 'Insert' in the designs, and in our recent user test the 'apply changes' button was confusing to one user.

Agreed with Johannes: When hitting the 'Replace citation' button, the user likely expects to replace the whole citation. It makes no sense trying to insert an automatic ref or CS1-templated ref into the subref section of a reference, since those are only suitable for main refs.
So when pressing the 'Replace citation' button from the Details Dialog, the whole reference should be replaced, not only the sub-ref section of the dialog.

Thanks for including the mobile design! I think I need to make a different approach for mobile, it doesn't work well like this: the relationship between the 'edit' (pencil) icon and the reference now gets a bit lost because of the chip in between. Would it be difficult to place the chip differently for mobile only? For example stuck to the bottom of the ref content?

Also, the padding within the InfoChip seem off, this is the codex design: https://doc.wikimedia.org/codex/main/components/demos/info-chip.html

We could ask for a shorter string for the reused chip, but that feels strange. Maybe we should go with the other approach per default, to always display the chip below the edit button:
desktop:

mobile:

Patchdemo: https://9a196aac3b.catalyst.wmcloud.org/w/index.php?title=Hauptseite&veaction=edit

Looks and works well! A few minor points:

1. The first time the subref dialog opens, it somehow has a lot of extra height and whitespace
   
   . If I close the dialog without adding a subref and click on the 'Add details' button again, the whitespace is gone. Is this a by-effect of the onboarding dialog?
2. The blue link underneath the input field in the subref dialog does not open a new tab.
   

Thanks for bringing this up @Amire80! You make a really good point that we had overlooked so far. I agree with your suggestion to complete the sentence.

Update after discussion with @awight:

Makes sense to disable the ref-edit button indeed. Will definitely also need to figure out how to deal with this edge case if we go with the Combined ref&subref dialog...

Added new message texts in the doc, and some extra comments. I skipped one (the follows= error message) because I did not fully understand it. I also added a few messages that were not in the list yet, for which I don't know if we can/should add them at this stage for the MVP. So before implementation I think it would be good to review them together with UX & Eng (and PM if implementation of the messages would lead to additional workload/complexity).

Ah yes sorry I could have been more clear: I think it can be merged! It is a clear improvement over the current situation without the patch.

Sorry I missed your comments here completely somehow.

Thanks for thinking it out in so much detail @thiemowmde!

Definitively an improvement now that the name does not interrupt or overwrite the content of the reference. I am doubting about the space and prominence the name gets though: to most VE users, the name means nothing, and is an element of the reference that they can not see or interact with anywhere else in VE. There is no way for them to find out why it is there and what it means, but it is very prominent in the re-use dialog now. Could we hide this functionality (to show the name in the re-use tab) under a preference or something, so it is accessible for advanced users who want to use it, but it will not confuse users that have no clue what a ref-tag and refname even are? If not, we should probably develop a better way to incorporate the concept of refnames into the VE editing experience. Do we know if this function is currently essential to any users?

In T367177#9943579, @awight wrote:

Would be interesting if these [book referencing] examples use "the" cite book template.

The answer was that dewiki is the exception and in our sample bare refs are created. But on other wikis the book referencing is normally done using templates like {{sfn}} (or templates with even more magic included).