I saw others asked the same question and the answer was always “not possible”.
What to do when you want to have a day and night cycle in your game? There is no way to hold a lightmap as a separate entity and just swap them at runtime. You have to maintain two levels and then load them depending on the daylight cycle. I’m not even talking about a sun that moves constantly, more like a fixed number of prepared settings that have their lightmaps fixed which can then be swapped at runtime.