Show current headspeed and tailspeed (+harmonics) in the FFT spectrum view

[rotorflight]

The spectrum view should clearly show what the headspeed is (+tailspeed and harmonics)

NOTE NOTE NOTE NOTE. The headspeed varies throughout the log. The spectrum view (FFT) is calculated over the selection, and the headspeed is never constant. Thus, the headspeed indicator in the FFT should be a range.

Maybe a coloured area for the headspeed variation in the selection would be the best. With numeric values showing min, max, and current value under the cursor.