Inventory management in this game is a nightmare. It should not be a skill that you have to obtain to sort your bags. I don't think giving this skill to everyone would unbalance the game at all.
I remember having wanted a way to sort my bags for a long time. Then came bag search. Now that the sorting upgrades exist and I bought them... I don't use them. It's just too convenient to use search... even if the item I'm looking for is in the bag I currently have open.
I've tried to love the sorting upgrades, but the predefined categories it has are never useful for me.