How Do I Create a New Mailbox Like the “All Inboxes”, “All Bins”, Etc.?

Can I create a new folder/mailbox like the “All Inboxes”, “All Sent”, “All Junk” etc., i.e., one that would have separate subfolders per email account? I operate three email accounts with Mac Mail (and that’s great!). As I go through my incoming emails in “All Inboxes”, I would like to enhance and systematize my email […]