LockSmith will pop up a button on your screen when you have a locked box in your inventory. Click on it to unlock the box. If you have more than one locked box, keep clicking on the button to unlock all the boxes. Once you have no more locked boxes, the button will disappear.
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CrowBar, which does the same thing, but for openable containers (including unlocked boxes, clams, dungeon reward bags, etc.) instead.
I prefer this approach over Molinari, since I don't have to look through my bags to find the box/container, and I don't have to be paying attention to notice when I get something I can unlock/open. I would recommend Molinari for disenchanting/milling/prospecting, though.