I use TARGET for the curves on my joystick.
You set the curves (and other things if you wish) then save the file.
You have to run the file before you start Elite, which is a nuisance, but it does mean you can have different curves for different ships; you just choose which file you want to run.
Others have mentioned TARGET. This is a great piece of software (I use it myself) for Thrustmaster sticks only, and it can't be used on the T-flight HOTAS sticks.
If you have a T-flight, or any other low-end stick, you have two choices - Joystick Curves or Joystick Gremlin. Both programs use vJoy to alter the response curve of the joystick.
Note that you will need to remap your axes once you've got your curve set up. Be careful to use the "test axis" option rather than move the stick, as moving the stick will result in that being mapped rather than the virtual one.