The feature is ported from Better Brightness Slider

Ported the mod from the lower version 1.20.x to the NeoForge version 1.21

Better Brightness Slider expands the default brightness slider, making it range from -100% to 1200% (fullbright) instead of 0% to 100%. It's a clientside mod, so it isn't required on servers.

Upgrade version to 1.21 NeoForge.

The mod should be compatible with Optifine and Embeddium.