You can just drop items and they'll be permanent unless the area becomes inaccessible.

For example, I drop crafting items on the ground inside the smithery in Arnika because that's where I'll be using them later.

Thanks. too bad they didn't allow for bank storage. They even have the bank designed.

You can put things back into any chest and the game keeps them for you... be careful because items stored in a chest DON'T count for quests so you may have to go get a certain ball out of a chest to finish the game or enter an area.

p.s. Yes even items that you can't drop can be put into a chest... just remember which chest or on your own head be it.

I don't get your problem with the bank vaults. Once you've gained access, you can use the elevator whenever you want.