Fingerin Number on Fretboard

As a workaround, you can add ordinary text (bold here). It's another display - below the fretboard, not within the dots -, but not uncommon at all. And by using always the same scale for your fretboards diagrams, it's reusable (after put them in a custom palette)

EDIT: Of course, it's time-consuming if you do it on every fretboard diagram. In this case, it may be legitimate to show in a vertical frame, under the title frame, all the fretboard diagrams encountered in the piece (let's say a dozen or less) with this display - as a memory aid -, and then not in the score itself. An idea (only a workaround, I agree)