Offline rendering systems almost all include the concept of ‘portal’ lights - rectangular light-like actors that can be placed in doors/windows to ‘focus’ exterior GI into the interior, with optional intensity / color modulation.
This is super handy for maintaining natural looking lighting, while reducing EV delta between interior/exterior spaces when dealing with combat heavy gameplay where visibility is a concern.
It’s also a nice tool for art direction.
My understanding is that they modulate any ray passing through it, allowing you to multiply the intensity of the ray or modulate the color. I’m not sure the concept works out of the box with UE’s rendering solution, but if we could have something similar to this, it would be a godsend for natural (non practical) lighting.