The tmd file is the right place for that.
Just open the tmd file of the aircraft with a decent text editor (e.g. the free Notepad++), then search for "Flap" and you will either see a servoclassic called "ServoFlaps" or just "Flap" or "Flaps" that usually uses the "FlapInput.Output" or "FlapMapping.Output" or "FlapLever.Output" as a target. The servoclassic is a polynomial with
Usually we only use the linear P1 part for the flaps, so for any given input from 0.0 to 1.0 the output is just the product of the flap "p1" and the input. That means if you increase P1 you will get a larger deflection. That's the quickest way to get to a larger deflection, though that is not actually the correct way because the flap positions are needed "outside" of the aircraft, for example for the flight info bar at the top, the autopilot, when switching aircraft, etc. So just increasing the flap angle already can affect things like: when I switch from one aircraft to the next, how much flap will the next aircraft have at initialization.
But for beginners, sure why not