Style placement "Above/Below" needed for String Number
See explanation for why this suggestion is wished: https://musescore.org/en/node/283209#comment-892172
And (good) reasons: I explained its usefulness in another thread (I don't re-find it immediately).
I was saying that most of the string numbers are related to strings other than the first one: to indicate alternative fingerings on another string, from 3 to 4, or 4 to 5, etc.
And so, in a polyphonic/multivoices context, these notes are in Voice 2 or 3/4, so most often within the staff for an intermediate voice, or under the staff, for basses.
That is to say these strings numbers are, the most part of time, located below the staff, and not above, as the current behavior.