The question doesn't have anything to do with GSX which, as explained on the manual and as discussed so many times on the forum, is entirely unrelated to jetways, and doesn't change ANYTHING in the way they operate.
That would be more of a scenery question so, if your question was about jetways in default sceneries or FSDT sceneries and the vast majority of 3rd party sceneries that have standard animated jetways, that's very simple: the default FSX jetways animation system that all these sceneries use, supports only one jetway that will connect to one door. Any double or triple jetway you might see in a scenery, it's a static one.
FSDT KJFK has an exception to this, and has a working secondary jetway on the A380 gate, which is controlled by the FSDT YouControl menu, and works ONLY if you are in an A380.
