As explained many times already (too many times to count, really, there's even a blue highlight on the manual), GSX doesn't control, doesn't affect, doesn't change, is not affected by, anything related to jetways.
They continue to work (or not) as they always did. Installing GSX won't change anything about how jetways operate. The only form of interaction, is that GSX can detect if a native FSX jetway is present on a given parking, by looking at the scenery AFCAD, or it can customized by you, to indicate which parking spots have jetways, if you use a scenery with static jetways which can't be detected automatically.
The GSX airplane editor, like anything else in GSX, doesn't have any relationship to the jetway, it's used ONLY to indicate to *GSX* where the airplane doors are and what they are used for, so that GSX can place the correct vehicles in the right places.
The jetways is handled by FSX, and FSX doesn't know anything about the GSX configuration. The only way to affect default jetways, is to edit the door's coordinates in [Exits] section of the the airplane.cfg
