TL;DRAbility to insert items into restricted (red) spaces inside of chests.
What ?Let's take your typical Yellow Belt and place them inside of a box. Let's say that you've told the inserter placing them in the box, that half of the box is not to be filled, by using the X limiter and turning half the spaces red.
Now, the box has been filled with what it's permitted to hold of Yellow Belts, but you have a few hundred you'd like to get rid of in your inventory. Normally you could Control-Click and deposit your items into the box, but currently you cannot, because the rest of the spaces are red from the X limiter. So to remove your belts and place them in the box, you have to un-limit the box, which allows the inserter to immediately start placing items back into the box, while you then Control-Click to dump your belts. Then you have to re-limit the box.
How about instead, you can Control-Click once, and as normal, it fills up to the limiter, but Control-Clicking a second time in a short period of time (1 second?), would then fill the box inside the restricted area as well, EXCEPT FOR spaces which have been restricted for specific items different than what you're attempting to deposit.