I think it would a great addition to be able to designate retainer tabs for specific item types. This way it would be a quick way to dump mining materials off when I have already designated a tab on retainer #1 for mining. Doesn't seem like a far fetched idea when nearly everything is already classified by a category anyway. It would also be beneficial to be able to drop items off on a retainer into the current tab selected rather than it defaulting to the first available slot.