I would find it useful if I could list the items included in one vault (e.g. the Personal Vault) and not in another vault (e.g. the Primary Vault). The reason being that, I've occasionally used 1P mini to add login credentials to one vault and have mistakenly used my Personal Vault instead of my Primary Vault at times.
Other users may find it useful to list items appearing in both vaults (intersection) or the list of distinct items appearing in both vaults (union). Just a thought.
1Password Version: 7 Beta
Extension Version: 18.104.22.168
OS Version: OS X 10.13.4
Sync Type: iCloud