For example the CRJ got its own stairway and calling a boarding the GSX staircase will go inside the plane's stairway, not looking good.
What CRJ are you referring to ? The Aerosoft one ? If yes, the *current* GSX configuration that comes with it already provides for disabling the staircase without disabling the door entirely.
If you use the Aerosoft CRJ, be sure you are using the default GSX configuration, not some configuration you made or downloaded because, in that case, the one you made/downloaded will take precedence over the GSX internal one, even if in this case the GSX internal one it's better.
The airplane configuration page will tell you from where GSX is taking the airplane configuration data.
If you are not using the Aerosoft, but another CRJ, please indicates which one it is, because we will need to add it to the internal GSX database, since the ability to disable stairs without disabling the whole door, it's not user customizable yet.