NOTATIO

There are other issues with slurs as well (for example, when writing a slurred quadruple stop on the violin, it attaches to the wrong notes and there's no easy way to fix it other than in the finicky Engrave mode.)

I could certainly adjust those slurs, but the work is so long that I'd probably spend a month just adjusting slurs manually.
I mean, there are points on the slur in Engrave mode that allow you to adjust angles and curves, but I don't have the best eye for that sort of thing.

Is this a bit better?
I'm not terribly good at this, so I need some guidance.

I think the problem with slurs is that there are simply so many possible permutations of the shape, depending on context, with so many elements to be taken into consideration, like accidentals, stems, beams, other noteheads, positions within a chord, etc...

maybe it's just so complicated that no engraving software has been able to incorporate all of the potential permutations a slur can have and manage to make it "pretty"?