I have seen a lot of "passwords" when mindreading someone, but I have not seen any point in wich I would have used any of them. For example the tree beneath the mill or the necromancer Naberius give a password to a storage. But I still can open any chests nearby, they just say I my lockipicking is too low. It must be something very obvious im missing since google wont tell me either, lol.

Passwords for storage areas allow you to get into the particular location. If you don't know the password when you select the door/hatch, you will not be able to get in.

To reach Naberius' storage area you need to find 4 parchments throughout Broken Valley and have them translated (which will let you activate a couple teleporter pads). The miller's storage area (talking tree mindread) is near the fortune teller, to the far west of Lovis' Tower.

Ah, I see. Thanks.