openmw.org

Sometimes I tend to collect a large number of loot, so it would be nice to be able to select more than one item to sell or move to a chest, similar to a file manager.

Here's an example of the functionality:

You mean holding [Ctrl] and [Shift] on click? (Although these keys are already bound to stack manipulation, so we'd need alternative key bindings.)
Doesn't sound that useful to me because you can already quickly buy and sell items by using said [Ctrl] and [Shift] keys.

However, stage-1 OpenMW will allow modders to create new item categories. A button to sell/buy all items of the selected category would be more convenient then (omitting equipped items and, maybe, quick key items), wouldn't it?

In Divinity: Original Sin 2, it gives the ability for the player to mark particular items as Junk in their inventory (placing a little icon on them when it is). Then when trading, there's a button that moves all currently marked Junk items to barter on them.

I've been really satisfied with Fallout 4's and Prey's buttons to get rid of all junk in one click, but then they're both games with recycling junk as a first-class gameplay mechanic and therefore already have junk tags on all otherwise-useless items.

The main problem I see with that is it relies on the developer predefining what you should and shouldn't be interested in. While for some things it may be obvious, it's not always (e.g. a steel dagger; in the early game it's potentially rather useful, but later on it's junk to sell for a bit of extra money). Especially for a player-driven roleplaying game like TES, you don't necessarily want to predefine what is or isn't useful. For example, if you want to have to carry around a plate and utensils for eating (something you don't actually need to do, but you want to for roleplay purposes), you don't want to keep fighting the system to keep a set, but it'd still be nice to mark extra sets you happen to loot as junk to auto-sell.