A little background to make this easier to explain.
My current colony are degenerate flake manufacturers. When interfacing with a trader, I sometimes have more flake than he can afford to buy. If I click the double arrow, it moves all of my flake to his column, but then I'm giving a lot away for free. So I wind up having to do rough math to estimate how much to sell, then typing it in the quantity box, then manually using the arrows to increment the quantity one-by-one until I'm selling him as much as he can afford.
Long story short, I'd love to see a button that would only move as much product into the trade quantity as the other party can afford to buy.
I also miss this option. It would basically work the same as with caravan mass limit
It would be convenient. Meanwhile, use ctrl-click to move 10, shift-click to move 100 and ctrl-shift-click to move 1000.