Allow an existing email address under the main user account to be "moved" or changed to be a new account.

This should include the ability to take all emails that were sent to/from that email address and place them into mailboxes for the new account.

For example, someone has been using an email address for a business purpose. They have a Proton business account and created a email address under their account for use with business purposes. Later on they decide to create and account strictly for business use (that may need to be shared with an assistant). It would be nice to somehow just edit the email address by saying "create new account" using this address from an action on the email address. Assuming the same person will manage this new account, it could just be created and a password set without sending an "invitation" to some other email address. Or maybe even give the person doing this the option of just creating it or sending an invitation.