GSX does nothing for the jetways, it doesn't use, it doesn't change, it doesn't interact and it's not controlling anything related to how jetways operates, they are handled entirely by FSX/P3D and installing GSX won't change anything how they operate.
Configuring your airplane with GSX is only needed to control where GSX vehicles should be positioned, it won't affect jetways in any way, they works entirely separate from GSX, using Exits data found in the aircraft.cfg, and since the FSX/P3D jetway animation system doesn't know anything about GSX and its configuration files, any change to the airplane doors in GSX won't affect jetways in any way.