Levels

Didée's Ylevels:

a simple replacement for original levels mode, without clipping: input minimum at 40 and imput maximum at 220 will not clip the output to [40,220]. Values below 40 / above 220 will be scaled accordingly to the correct vales. This means, one can use any values for input minimum and maximum as "control points" without getting the input clipped at those values.

Didée's YlevelsG and YlevelsS:

apply the given levels conversion by 100% at Luma==0 and by 0% at Luma=255, and accordingly in-between.

YlevelsG does a linear sweep
YlevelsS does a sine sweep

Try those with gamma values 1.5 ~ 4.0.

YlevelsG (not YlevelsS) does "inverse" scaling for gamma values < 1.0,

Didée's YlevelsC:

Just try it.