Its not rly high prio as it depends how I think you should play the mod, which is making it dark for the dupes not for the player, which perfectly works.

I'm playing this with only slight darkness, so you see which areas are unlit but are not bothered by not seeing where you click (why would you want that lol)...

If you place lights where the colony needs it (not the player), that is everywhere you don't want the dupes to have negative impact from darkness, the colony will automatically look nice ...

Going into the dark will still have major maluses, that's why there is access permissions and lights on hats, lights on suits, different reveal/light ranges for dupes with different skills, etc... to be able to manage who is allowed to go out, as some new dupes might just die in the dark...

Due to the fact this is the only up-to-date mod that enables lower visual darkness, this should really be at least toggleable.

As for fixing the issue the most obvious solution would be to just make a second "visual" light layer which runs the same calculations, but for slightly larger light masks. Probably not the most efficient, but the most obvious, at least to me.

I'm currently trying a vanilla playthrough with the new DLCs and limiting myself to visual/QOL only mods. So I'm actually playing the opposite way that scitor mentioned - In this case I want unlit sections to be dark only for the player, not to have an effect on the dupes.

Really all I want is for the lighting to be more realistic in the game. It also drives me crazy that the vanilla ceiling lamps look like a round lightbulb yet only light up a strict cone beneath them. What were the devs thinking?