Mid point selection and shaping

Hi all,
I’v seen questions like this asked in some old posts but there was never a posted resolution. I’m not sure if I’ve found a bug, or if I have a setting turned off.
I can not select a line midpoint in a sketch, or snap two collinear midpoints together. I first attempted this on the iPad and assumed it might be a bug with the pencil, so I just tried this on the MacOS version and again no luck.
I know this has to be doable, without this ability sketches created for sweep features could not be constrained to a projected sweep path. The only alternative that I’m left with are workflows that are, at best, cumbersome.

What am I missing here?