Attached is a picture of one of my piano students' Bach Inventions (BWV 785). What does the +- mean? I've never seen it used before. A precursory search online revealed nothing. Sometimes a + indicates a raised tone, and a - indicates a lowered tone. This is all I can think of but it doesn't make sense in this setting if that's it.
I have seen + used to indicate an ornament, but I think this is an older sign from before Bach's time.
Also, the - could be tenuto.
But I don't think this is what they mean in this score. Try @Richard's advice and look for an explanation in the edition.
This isn't a direct answer, but it may be helpful...
According to IMSLP this is the measure from your question in Bach autograph...
...is a well known guide to ornaments also in Bach's actual writing.
Whatever those marks are supposed to mean they aren't Bach's. Same goes for the expression markings. It seems worth noting those things are someone else's additions and are not Bach's instructions.
I don't know this symbol, but I think it would probably be an indicator of either volume, as it is near that crescendo, or fingering. Some guitar sheet music will use + and - for position shifts (if you need to go up 3 frets with your 1st finger, +3 is indicated at that note). It could also be indicating a slight variation in tempo, as in specifying the rubato.