I'm not sure if there's a standard definition for "motion retrigger interval," but I'd check the manual for your device. Look for the Z-Wave parameter information--I assume that's what this is--to see what they say. One I randomly Googled (Aeon TriSensor) has such a bad explanation that I can't even figure out what they mean other than the fact that it's different from "motion clear time," which sounds more like what you're looking for. But who knows (someone, I'm sure, just not me).
You can definitely play around with this to see if you can get what you want to work, but my guess is that you might not be able to get exactly what you're looking for. Most motion sensors are designed to detect motion in a whole room, so if you didn't get a "curtain sensor" designed explicitly for the purpose of detecting a narrow field (like a doorway), you might have to use one of the "hacks" (heat shrink, etc.) to create the same effect with your sensor. Perhaps you've already seen that and have--just wanted to make you aware if not! Given that most sensors are not like this, most people also configure their lighting automations around this behavior, as well--e.g., keep the lights on as long as motion is detected, turn them off (usually after a delay since not all sensors are sensitive enough to constantly detect motion even if someone is in the room) after motion stops. In your case, it sounds like you'd maybe want to change the scene to something if "motion inactive" isn't sent within a certain timeframe, just to think of an alternate way you could do this automation if the original idea doesn't work.
Again, if your sensor works for this purpose, there's nothing stopping you from creating an automation around that behavior--it's just a bit uncommon around here, and I don't mean to discourage you from trying but rather just make you aware of some of the reasons it isn't. Good luck, and I hope something ends up working the way you want!