Sorry if this has already been brought up, but I find the use of sliders to trade a certain amount of goods quite tedious, especially when trying to adjust the quantity one by one.
Sure, you can type in the number you want (when it’s working, seems like on certain setups it doesn’t).
I’d find much more easy to have buttons to add or substract a quantity. For instance, a + ou - (or arrows <>) in front of the item, which would increase/decrease the value by 1, and using ctrl + or ctrl - would do the same by 10.
Cheers !