Storage: Allow separate "Output only if above" setting per-output port, to aid in overflow disposal
The blue "Output to belts/pipes only if above" slider on storage buildings should optionally be settable per-output port. For example, "Output left only if above 180; output right only if above 0". Alternatively, if it's simpler, it would be fine to have checkboxes to only apply the limit to some output ports.
A common scenario is that a recipe produces a byproduct which is useful, but may need to be disposed of if overproduced (for example, half the products in the early-game oil industry). Ideally, I would like to use as much of that product as possible, and store up a buffer if I can't use it. Then, only once that buffer is full, burn or dispose of the excess. It is difficult to achieve this behavior in the current game. With my proposed solution, you can just say "Output left (to the flare) only if above 180; output right (cracking) only if above 100; store the rest for trucks."
This could also be handled with logic mechanics, but this solution seems simple and natural.