Add the ability to easily take just one unit off a stack in inventory.

In the inventory window, if you have no items held, a single CTRL+right click (or whatever) on a stack of items should let you take just one unit off the stack. On mobile, there should be a toggle icon that cycles between 1 and 50% and maybe a couple other options. It could be a roller control that you swipe up or down on to change the setting.