How to set a minimum throttle for an engine, yet shut it down with X?

[Kerbal01]

I attempted to edit the Merlin 1D from Laztek to include a minimum throttle of 152 Kn from 400 Kn (about 40% of max, what the real engine is capable of). The problem is I need to be able to shut the engine all the way down, to 0kn. Is there a line like MinThrottle, to differentiate it from MinThrust, to accomplish this? Or will I need to use action groups? If so, how do I set it up?.

[NathanKell]

Needs a plugin. RF does it, for example.

[Kerbal01]

Is there documentation how to add the module to the .cfg of an engine?