I’ve realized that there is a slightly cleaner way of implementing the workaround I described in my previous message.
Instead of modifying a standard Entry Type, such as “Unpublished”, it is better to create an entirely new Entry Type in the Custom Entry Types dialog. In the screenshot below, I have named this new Entry Type “Custom1”, but any valid name that doesn’t clash with an existing Entry Type would do. Then simply add the “citedby” field to the Custom1 entry type, and set it to “Multiline”.
As before, the “citedby” field is then automatically wrapped for all entry types, and it avoids having the “citedby” field appear in either the Required or the Optional Tabs for any entry type except “Custom1”.