Hi,
I was wishing to superscript the -1 after ms-1 ( metres per second). I used the superscript icon within Character dialogue window. Whilst the 1 was superscripted, the minus sign was not. Upon further investigation, I found the same problem with plus sign. In addition, when two letters are selected neither of the will be superscripted. Further, I found similar problems with subscripting.
Test data: ms-1, ms+1, ms ?1, msaa.
The number characters are superscripted, letter characters are not.
This is reversed for subscript.
Arial was the font used.
This works as it should for both super and subscript in Affinity Designer and Photo.