The inventory can be sorted and filtered, which is great, but I had a few suggestions for the inventory/equipment system (as of Patch 8).
When equipping a particular slot (say the currently selected character's weapon), I love that the inventory filters only to items that can be equipped in that slot. I think being able to sort by damage in this context would be extremely helpful.
Some type of indicator to indicate a collected piece of gear is better or worse than your current item would also be a huge quality of life improvement. Maybe a small up or down arrow placed in a different corner from the "E" showing the item is equipped by someone already.
Also, there is equipment that each character is not proficient in. I like the option to equip those items, but an indicator (maybe an orange border or shading in the same color as the tooltip for this) would help to highlight that the character is not proficient in the item without having to go to each item and read the tooltip. Perhaps also an ability to filter out non-proficient items.
Incorporating all of this would then lead to, for example, when you click on the weapon slot for the current character, you can then sort by damage and see at a glance which items are higher damage than the current equipment and which items you are currently not proficient in.
