@kkjj One of the parameters that most influence the "feel" of a dark night is the static lighting, lowering other values without lowering the static lighting value will result in a terrible image. But here is the thing, when very low values are used, some places become totally dark, creating an undesirable contrast in the environment, so making the nights too dark will cause problems, and even if you only change the color correction to decrease the brightness, it will still have side effects, the game will get darker but it will also become more and more opaque as you lower it, not to mention that this will affect the entire screen, which means light sources and another things. I know this because at first I tried to make the nights darker, in the end, I realized that it is not worth it, the nights of this timecyc are a balance between dark and bright, not too dark but also not very bright, if you really want more darker nights, and do not mind those side effects, download the "In-game Timecyc Editor" and edit the nights at your own risk, I do not recommend it, but if you really want it, go ahead.
@ZL1 Update: After some tests, I realized that it is not possible to greatly increase the opacity of the dynamic shadows by the "In-game Timecyc Editor". If you really want this, I recommend using "Mix Sets v3.0" and look for the "ShadowOpacity" option, it will increase (or decrease) the opacity of the dynamic shadows considerably.