This might sound ridiculous to you but in the U.K. we generally don’t have tilting windows. They are really common in Germany though.
The AC unit is a little different than "traditional" window units. There is no slot or anything really to grab on to the window or the sill. It is mainly secured by a brace that is also not screwed into anything really, just directing the weight of the external portion of the unit into the side of the exterior wall.