How to flip sixteenth note between staffs

see https://musescore.org/en/handbook/cross-staff-notation

If I understand correctly, you already have what we see on the left, but you wish it to look more like what is on the right. That's not standard, at least among modern engravers - in fact, the main reference work on the subject specifically calls attention to these "beam corners" as something to avoid. So we don't provide a ready-made way to do that.

Someday we may consider additional properties to customize things like this, but for now, I'd recommend just heeding the advice to avoid those corners, and leaving this at the default.