It would be nice if we could filter the available and installed extensions based on criteria like overlay/panel, info/widget/game, or related stream content.
Definitely this. Just scrolling through a seemingly unorganized list to browse extensions is really clunky and will become increasingly frustrating as more extensions are added.
Bang Plays Games commented
I would like to see a "Loadout" feature for the extensions. Build your loadouts based on the game title, then when you stream that particular game, Twitch automatically applies the proper extension loadout.