When I trade in the later game I often end up trading 1 piece of every special resource (and sometimes also 1 of the "normal" resources like Elerium) with my trade partner since only the first resource brings relatively high yields, while every further resource of the same kind seems to gain exponentially less. So I have to click on the resource in the left-hand list, then I have to click on the right arrow in the amount window to bring the amount to 1 and then I have to click "offer" for about 10-12 resources every time ...

It would be great if you could shift-click or ctrl-click or whatever on a resource on the left-hand side to automatically add 1 piece of that resource to the trade.