So one of the most important things in this game is being able to loot fast, and after seeing a few streamers play I was wondering how they did certain things. I was unable to find any guides or anything that provided solid answers so i just experimented until I figured a few things out.
Folding a stock: On the weapon you are holding, alt-L folds a stock in game. However if you are just moving an item around in menus, middle mouse clicking on it folds the stock.
Double clicking quickly on an item that has interior space opens it.
Middle mouse clicking on an unexamined item examines it.
This has nothing to do with looting but you can put a visor up and down with N, it is the same binding as NVG's.
Those are the ones I know. If you know of some of the other menu hotkeys, specifically ones to quickly inspect an item, please let me know.