Better yet, change keys and chests/coffers:
Make keys into "potion" type items with a single charge. Using that charge adds the key to your "Key Items" list (like Delkfutt's Key) (Once a key's charge has been used, it should disappear like a potion.) I'd suggest a new "Key Items" sub-section: "Key Ring"

Allow trading a key in your inventory that still has a charge to the chest to open it, OR allow it to remove the temporary key item from your "Key Items" list to open the chest when you select the chest.

The only balance issue in this case would be allowing players to hold onto the Temporary Key item as well as an inventory key, allowing someone to open two chests without farming in between. This could be addressed by not allowing the key to drop if you have the temporary key item.