When you run F/A-18C profile, have imported device mappings for a keyboard and Thrustmaster Combined and have assigned TM Combined keys 30, 31 and 32 as modifiers, then all should work as intended including Idle/Stop detent. It will work just like that. If you have some undesirable behavior, then check if you have TM Joystick and Throttles visible under Controls (sometimes mine doesn't get switched off while running the script). If so, then clear all the mappings assigned to them, and you should be fine. Another thing to check is that sometimes rudders can have something undesirable assigned to them so check that out also.