What do I have to do to to be able to use Luminance and Uniformity?
HSL- Saturation is active, but Luminance and Uniformity are greyed out?
If you just activate the tool, the global (white) dot is selected by default. When this is selected, the Luminance and Uniformity sliders are unavailable. Once you select one of the coloured dots, they will become available.
Thanks for the solution zkarj. Now they work.