User`s manual

Reference: The Advanced Image Correction tools 93
Saturation tool (LCH color mode)
Select Saturation method.
"Curve" is the default
Select Saturation Range.
"All" is the default. Other
selections let you change
the saturation for Highlights
only, Midtones only, or
Shadows only
Drag the curve above the
default diagonal line to
increase saturation. Drag the
curve below the default
diagonal line to desaturate
color into gray levels
The Saturation Curve tool lets you increase or decrease the color intensity
(chroma or saturation) of an image without altering its hue and lightness values.