There are more than 500 Quest items in the game, and we have only discussed a hundred of them. But here's the thing, some of them are event-exclusive and don't exist for a longer duration in the game. Some Quest items you will receive after completing some quests but still don't have a use in the game yet. Maybe it's possible that Genshin Impact will launch new quests in the future where we have to use Quest Items obtained from the previous ones. That's just me being optimistic and really hoping that something like that happens.