Nevermind I figured out,
visually editing them like this makes easier to achieve desired shapes
export(Curve) var bezier
when you have some shape you want, you save it as a .tres file
then to load them you either use load or preload
var stored = load("res//path/file.tres")
or
var stored = preload("res//path/file.tres")
and finally call it by its name, in this case I used it to interpolate some values from linear to exponential
var get_new_value = stored.interpolate(range_lerp(some_value, value_origin, value_ending, 0.0, 1.0))