I almost enjoy the functionality of the “Unified Inbox”. I would enjoy it much more if it actually unifies all of my accounts!
Currently, I have 3 individual accounts. Only 2 out of the 3 are included in the view. To view the mails in the other, I must switch to its own unique Inbox.
Including the inboxes of all accounts should be the default behavior. I don’t know why it’s not working for you. If you have a suspicion please let us know.
You can include/exclude a folder under Manage folders > [Folder name] > Unify.