I realize some people have very specialized needs when it comes to rate/curve settings.
I want to avoid feature creep and cluttering of the interface as much as possible though. I'm not saying it will never be available, but at the moment it's not likely to be there anytime soon.
My suggestion to those who have special rate/curve adjustment needs is to use a linear curve setting in Freerider, and adjust the curve exactly to your liking for each channel in the menu of the transmitter itself.
In FPV Freerider Recharged you have the full level editor so that you can create your own tracks. It is not possible to change the built in levels in the desktop version of Recharged (the forest, factory, carpark etc.) though because they use a completely different level creation method.