Casement window owners: how are you venting?

I’ve done some pretty extensive googling and there doesn’t seem to be a great solution for venting to a casement window. Ideally, I’d be able to either lock the window to the vent width (could print a vent that goes from round to narrow-ish) or have it easily removable so I could close and lock the window normally.

Has anyone set this up in a way that works well for them? Sliders are just infinitely easier to deal with…