I have added a custom PB in two airport, from one stand (not from all the stands), and now from all the stands of these airports i have only the straight head PB and the custom PB...normal left and right are not available. Is "normal"??
You must have had all the parkings selected, or the "root" node of the left side of the page (the one that contains the ICAO code), so your preference was applied to all parkings. In this case, yes, it's normal, that's how GSX is supposed to work.
You can undo this by removing the .INI file for that airport in your %APPDATA%\Virtuali\GSX folder
Another question: is possible to deactivate the sound of the vehicles when the visual is from the cockpit ?
No.
The whole point is that GSX supports surround sounds, and in the cockpit is where the effect can be heard the most. Since you are boarding/deboarding or doing catering, the airplane doors are open, so it's normal you hear them.
Of course, you can control the volume with the GSX sound volume slider.
