As explained on the GSX manual, and discussed many times on the forum, jetway operations are entirely unrelated to GSX, and nothing in GSX affects or changes the way that jetways operates.
The only interaction GSX has with jetways, is that it checks the scenery that is being loaded to know if a parking has one, in order to stop displaying front stairs and a bus.
This means, the door the jetway attaches to, can be controlled by changing its coordinates in the [Exits] section of your aircraft.cfg
