Hi Silentraven
I'm not with Laminar Research, just another flight simmer in the UK, but I had a look through the King Air C90B handbook supplied by X-Plane and there does not appear to be any reference to 'nose wheel control'.
However, my first thought was that steering under taxiing conditions would be done by the rudder and when I loaded a King Air C90B for flight in X-Plane 11, sure enough, I can turn a full 360 degrees within the width of the runway, just by using the rudder!
This is the same as the twin engine Beechcraft Baron 58.
Have I understood your question correctly?
Regards