It depends how your airport is made.
If the airport has proper FSX jetways, the marshaller is automatically placed closer, on the assumption that if there's a jetway, there's usually a building behind. If the airport has fake/static/non-standard jetway, the marshaller is placed in the best possible distance depending on your airplane eyepoint in the cockpit, so you have to customize it.
You might be able to speed up the process by editing your xxxx.INI file ( xxxx stands for the ICAO of the airport ) in the %APPDATA%\Virtuali\GSX folder, which is the file the customization option creates, it should be fairly easy to figure out the format (it's a plain .ini file) and just copy&paste many parkings.