Context
For the VisualDiff there's a separate mechanism to render the content build into the VisualEditor extension. For sub-refs we need to make that code understand the structure and number formatting.
Task
We already implemented fixes for the footnote numbers in the article text so diffs there are fine but the visual diff for the reference list does not understand the sub-ref numbering and formation yet. So this still needs to be fixed.
Notes
Most underlying code is there already to make this work.
Split from T397319: VisualDiff: Subref footnote markers show the wrong number