Slider on storages to prevent filling FROM belt too full

I would like to limit how full a storage will get from a belt, leaving room for truck drop offs. this would be very useful for cleaning out the shipyard, or managing deconstructions.
4th flag on the bar would be good symmetry, too.

Interesting idea. What I always do is setup a smaller storage with CAN IMPORT enabled, a bigger storage with CAN EXPORT enabled and priority to use the output of that smaller storage both for filling the larger storage and any downstream consumption.
It would save space to only have the 1 storage do all that and place it in-line with the output, now that we also have the means to keep a buffer in the storage.

added in 0.7.5c