It's getting really tiresome to select every single desk, locker and box for things. Specially since it might take up to a second to load the list. It just really starts getting on my nerves after a while. Is there a mod that would add a small box that shows all the contained items which I can see from even somewhat further away and I could also quickly select the items.

I look at something, press E from a few meters away, see all the contained items, quickly move through them with WASD (or just up and down) and select the ones with F or something and then I close it with E again.

At least it tells you if the container is empty or not, Oblivion did not do that.

I don't know of any mods that do this kind of thing, and honestly I'm not even sure if would be possible.

"inv" console command shows the items held by a container or NPC, so atleast pre-viewing them should be possible.

It sounds like it should be feasible. If you look at an object, a UI element comes up. Scripts can pull the list of objects in a container (not sure how leveled lists are handled, though). I'm sure it would then be possible to modify the UI element in real time to show the contents of the list, or otherwise create a new UI element. It could work on the same principle as the distance to aimpoint mod that's included in PNV, among others.