I agree with the issue, but the solution isn't that simple I think. There are multiple cases where doors have more than one key, sometimes as many as 3. I think once you use a key to unlock something, that key's tooltip should update to tell you what it opened. That way multiple keys with the same description would let you know they are duplicates. Keys with that unlocked could then all go to a seperate container so your inventory only holds keys with unknown purpose.
