I have a bathroom door whose frame is not plumb, so if the door is left slightly ajar, it swings fully open by itself. I want to be able to leave the door slightly ajar (about 4 inches / 10 cm) without having to manually adjust a doorstop or other device, just by using the door knob to leave it in the set position. I also want to be able to leave the door fully closed or fully open. It would be similar in concept to how car doors can stop in the half-open position.
Does such a device exist, that can hold a door slightly ajar?
I could kludge something out of a coat hanger wire and a nail between the top of the door and the door frame (see diagram below), but it wouldn't look great. Maybe there is a similar professional-looking product that I can install.