allow a superscript "+" to 5 in figured bass
There's a workaround (see https://musescore.org/en/node/234051#comment-753541), but a 5 with a superscripted "+" is (especcially for historic music) a common symbol in figured bass, see for example page two of the following link: http://abbasmacioglu.home.anadolu.edu.tr/figured-bass-symbology.pdf)
Comments
Just noticed, that the mentioned link doesn't seem to work anymore, so here the picture:
I would not claim that such a symbol never existed but, still, in some decades of dealing with music with basso continuo, I never met it, so it should not be "a common symbol", but rather a personal / local idiosyncratic version.
The "common" way to notate an extended fifth was "5" + "\": note the MS F.b. implementation already turns both the "5\" and the "5+" sequences into the relevant symbol.
In reply to I would not claim that such… by Miwarre
Example attached, from Schola Cantorum's GeneralBass Compendium... 5+ figure can be found also in one popular edition of Handel Continuo Exercises, and in J.S. Bach Johannespassion.