If you just walk away from an open container it should close automatically (though that isn't necessarily appropriate in all situations)... In Divine Divinity and Beyond Divinity right clicking would close windows in general, and for Divinity 2 right clicking container windows acted as 'take all and close'.
Yeah, the reason I want a quick close shortcut is for those areas where there are a lot of barrels and crates, and for I'm too lazy to just move away. A quick close would also be nice for books, inventory, really just any windows that pop up. Oh, actually, I've found right click closes stuff, just gotta click in the right spot, so never mind