[Putit]

Not to say I have any UI/UX experience or knowledge, but after regularly trading with merchant player almost on daily basis, I figured a change to the trading UI would be great. 

Currently the trading is the drag-n-drop style, and you can't select a group of items which isn't a big issue for people who just wanted to throw an item or two, but it becomes a Hellish experience for people who wanted to trade a big amount of items considering it took me +10 minutes to go through all the items, even worse when the items in your inventory starts to reach +150 ish since everything starts to lag. Ontop of that, the UI is also bugged (picture attached below, to replicate, just start putting items on the items-to-trade window).

Any sort of overhaul would be great, but if I have to suggest an idea for the trade UI, it would be an UI that allows you to mark items with shift+click/ctrl+click capabilities to make trading large amount of items easier, and an item amount value box next to the item with a plus/minus buttons. Lighter and desaturated color theme would also be nice, since right now the color is either really dark (trade UI) or eye-burningly bright (Char appearance change UI). UI and color theme examples below.