While you will find GSX VGDS listed in the Simobjects list in the MSFS DevMode editor, and you can insert them as well, they won't work this way, they'll just "appear" in the scenery, but not active.
To make them work with GSX, you must add them with a GSX Airport profile you can distribute with your scenery, which must be placed in the GSX profiles folder in %APPDATA%\Virtuali\GSX\MSFS
Of course, only users with GSX Pro will be able to see and use the VGDS but, the benefit is that it's completely free for you, as developer.