Ability to Favorite/Filter Stash Items
Basically what the title says. It's kinda frustrating having dozens and dozens of kinds of awakening gems and sig stones in the Champion Items tab and having to count the number of stars on each thing to try and figure out if it's a 6 star or 7 star awakening gem. That coupled with the fact that the ordering of items isn't consistent can make it hard to find things sometimes.
I think having a filter menu for Awakening Gems, Rank Up Gems, Sig Stones, or Ascension Dust and the ability to filter everything except ascension dust by Star level would just be a really nice quality of life improvement that shouldn't take an excessive developer time commitment.
The ability to Favorite certain items would be a little different than any currently-implemented sorting in the game, but could just function to let players select certain items that they want to appear at the top of the champion items stash so they're easier to find.