Inside of the shifter extension. One of these white plastic bushings should now be placed directly in the socket in the gearbox but I’ll be using a brass one instead to reduce play & extend life.
Here you can see the steel plungers on each side of the socket that bring the shifter back to the center (3rd & 4th gear) position. Playing with shims/springs (accessed via the cover facing downwards) will change the center return force.