Kdenlive/Manual/Effects/Colour Correction/Bezier Curves
Bezier Curves
This is the Frei0r-curves filter by Maksim Golovkin and Till Theato.
Adjusts luminance or color channel intensity with curve level mapping.
See TheDiveo blog for an example of how to use this effect to colour grade clips.
Curves is also an interface into this frie0r filter.