The feature to automatically recognize embedded staircases is supported, but its customization is not yet available in the user interface.
However, you can create an embedded staircase that always work, it's just that it won't be recognized automatically in case you alternate between using the GSX stairs or the airplane stairs. If you enable the embedded stairs, GSX won't send its own stairs anymore so, the lack of the "automatically detected embedded staircase" feature, will simply means you'll HAVE to remind to open the airplane own staircase, otherwise passengers will float in the air.