Okay, but can we talk about how annoying it is that the Left/Right arrows are reversed? Without fail, every time I see this captcha, I click the wrong arrow first.
My bet (or hope) is that items stack with each-other still, even if they're of differing quality. Maybe when you hover over a stack of items in a slot, it'll show how many of each quality you have, and you can select/split specifically?
Though, inventory size is supposed to be further increased by higher-quality modular armours, which may also help...