Hello. I have the same issue, but there’s a workaround:
- Start a new flight, but set the starting departure location to a runway.
- After the flight loads, retract flaps and shutdown the ATR’s engines.
- Next, use GSX (or an equivalent) to reposition the aircraft to a gate.
When restarting the ATR’s engines, the idle will stay above the required min %.
The downside here is that you have to do this for each new flight.