Context
When editing a ref from the references list the convert button on the edit dialogs lead to unintended behavior see T367910: The entire reference list is deleted when attempting to replace citation with a reused reference. That's why we disabled it for these cases.
See
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cite/+/1223680 &
https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Cite/+/1219863
Solution
We could re-enable that button when we're sure that the references can be edited without replacing the reflist. This could be achieved by making the actual edit independent of the selected node. In the problematic use case the references list node is selected although we want to edit and replace the content of the related reference node / it's internal item.
When T413760: Allow MWCitationDialog and MWReferenceDialog to work on refs that are not selected is resolved this should be possible.