While the current stash tab system is very good, I think it could help a lot for stash clarity to have an optional intermediate group level.
For example, a player could have as the top group “Collection” for stuff they want just for the sake of collection, then as intermediate groups “Uniques”, “Set”, “Legendary”, etc…, then as tabs in the “Uniques” intermediate group, they could have “Body Armour”, “Belt”, “Helm”, etc…
I think it would be especially useful for players using a lot of tabs : when using over a hundred tabs, simple grouping isn’t sufficient to keep the stash legible. As is, at best you’ll be able to have a 14x14 grouping (196 tabs), which still isn’t very usable, where a 4x5x10 grouping would prove way more efficient for navigation.