In Mail.app on El Capitan, the Mailbox menu offers the menu item
Use this mailbox as. A submenu offers the items
Trash Mailbox, and
After using one of these commands, the selected folder disappears. That folder's name is masked, displayed under the
Archive icons at the top of the sidebar as the name of the account rather than the actual folder name.
How can I tell what is the currently designated folder for each function (Drafts, Sent, Junk, Trash, and Archive)?