Slope represents center-stick sensitivity. The value is scaled such that it's equivalent to RC Rate when no Expo is present.
Shape interpolates between a curve based on Super Rate, and a curve based on Expo. While adjusting, Slope and Max deg/s are unaffected.
OpenTX Expo refers to the expo curve on an Open TX-based tranmitter--typically zero.. NegativeOpenTX Expo adds a few interesting possibilities for adjusting curve shape.
If Super Rate value is red in color, a negative OpenTX Expo is causing a non-increasing slope. To resolve, Super Rate should be increased.
Checking the Derivative-box plots the change in Slope versus stick position.
FlightOne/Raceflight conversion offers fits based on minimizing average error (Methods 1,2,4) or minimizing the single largest error across stick travel (Methd 3). Methods 1 & 3 are constrained to fits within +/-50% of the source initial slope, whereas Method 2 constrains initial slope to within +/-10%. Method 5 is based on closed-form equations which exactly match center-stick shape and Max deg/s.
Method 2 (Narrow search) is the recommended method for FlightOne/Raceflight to Betaflight conversion. Each approach has merits and drawbacks, this approach being a good compromise between maintaining center-stick "feel", while not grossly misrepresenting latter portions of the curve.