Vaults within vaults

So I was wondering if you can put an encrypted vault inside an encrypted vault?

I tried it but something went kooky and ended up making 2 entries in the taskbar popup menu for the inner vault, neither would allow me to mount and unlock even if the outer vault was mounted and unlocked and there also was just a normal directory with the same name as the 2 entries inside the outer vault.

Is this not possible or did I just mess up the setup?

What I want:
Vault 1(password 1)
├─ Vault 2 (password 2)
│ ├─ Encrypted files only accessible with both
│ passwords
├─ Encrypted files, etc…

What I got:
Vault 1 (password 1)
├─ Vault 2 (password 2) - won’t mount
├─ Vault 2 again (password 2) - won’t mount
├─ Vault 2 (normal directory, not encrypted)
├─ Encrypted files, etc…