Allow us to Tune them based on the resources we got at the time.
Basically allow us to choose which conveyors gets the most resources/items at a time. I've had many countless times, where one smelter or one constructor are overflowing but the other conveyor is lacking and so i'm losing efficiency bec of one constructor only requiring one while the other needs two. If you could just reduce one channel to like 25% instead of a 50/50 it could really fix these annoying issues.
This means i don't have to make more miners or smelters just because the splitters are unfairly distributing resources.