Mac, Apple keyboard with numeric keypad.
I wanted to use F18 to start slur and F19 to end them, but for some reason neither of them work. No problem assigning F18/19 to other commands.
Then, I assigned F16 and F17 to start/end slur, F16 works, F17 doesn’t. I did figure out that it wants the SAME key with shift to end the slur, so Sh+F16 works, but but but… it’s a stretch for my little hand 
thanks
Alex
Unfortunately, if a shortcut doesn’t work, there’s nothing much you can do about it, other than assign a different one.
Yes, F17 upwards don’t work, for some reason.
yeah, I enter notes with my left hand on the piano and the right hand on the keyboard, using the numeric pad section. So the less I have to reach other parts of the (typing) keyboard, and not have to use both hands, the more productive I am…
thank you
@benwiggy
actually they do, but for some reason not for slur. I was able to assign them to changing the grid resolution to 16ths and 8ths. Worked fine for those