When I played with this in the WordPress Playground example, I could not edit the citations from the Bibliography block (as noted in the line below the 2nd screenshot above) and clicking on the footnote number didn’t work to bring in the pop-up editor either.

Only clicking on the selected text in the body text block brought back the pop-up editor, which is a very limited pop-up that could be harder to navigate for longer citations.

No formatting tools are available to that tiny editor, which makes this of limited use if the citation format you’re following requires any specific text styles – italics, smallcaps, etc. I suppose you could copy and paste in citations, but editing them looks more cumbersome than I’d hoped from this writeup.