You asked, we delivered! You can now set an extra password for Proton Pass in addition to your Proton account password, allowing for better compartmentalization and peace of mind.
Be sure to store your extra password securely. Rolling out now and available for everyone in the coming days: https://proton.me/support/pass-extra-password
This feature is rolling out today to all Lifetime plans, followed by a staged rollout for Unlimited plans, and it will be available to everyone else over the coming days.