We are working on several user interface changes that affect jetways so, the option is still there, but cannot be set with the parking editor UI as it was before.
But you can still control the appearance of all stairs on a jetway-equipped parking, by setting the
hasjetway = 0
line, for each parking you need to set this, in the airport .INI file, located here:
%APPDATA%\Virtuali\GSX