What type of window is it exactly?
A lot of people just treat these like patio doors and put A bar or a lock that keeps the window from opening past a certain point.
After that, you have a couple of options, but it depends on exactly the layout of the window. You can put a tilt sensor on the bar. Since the bar has to be moved to open the window further, you get an alert from the tilt sensor which you then react to based on mode and security arm status.
Of course this doesn’t help you if someone just breaks the window, but then your open/close sensor doesn’t help you with that either.
There are some bounce beam sensors that can trigger if something moves too far in one direction, but again, it depends on the exact design of the window.
Sometimes a curtain motion sensor can catch the motion of a window as it comes in one direction although to be honest it’s more likely to catch the motion of a person’s arm opening the window. These work in some set ups but as I’ve posted before I don’t like motion sensors put right against windows. You get too many false alarms from temperature variations.
I’m sure there are other options, those are just the ones that occur off the top of my head. A tilt sensor on a blocking bar is going to be very simple and can be easily integrated with SmartThings. But it won’t fit all window set ups.
( by the way, I’m assuming that this is a window that you often open all the way during the day when you’re home, and that’s why you don’t want to install a window stop. But just in case someone finds this in the future, Amazon does have a whole category for window locks and stops. you’ll often find these locally in the baby proofing section. They don’t issue a report themselves, though.)