I'm not sure if this is even doable, and I don't have access to my computer at home to be able to check. What you can try to do (and I don't know if this would work, I'm just guessing) is in the GSX parking customization menu, multi-select the parking you want to modify, select the jetway, and try to do it that way. I don't know if that would actually work, though. More importantly, looking at your screenshot, I think this is going to be a tricky one since it appears you have some gates with single jetways and some with double jetways.