mailboxes disappeared
My private (non-standard) mailboxes disappeared from the mailbox list. They are is still on the disk in the Library/Mail/V5/B3B14FA1-F493-41C9-848D-15A4272B22C8 folder, while the standard (visible) mailboxes are there in the 625E30A1-F489-460D-96B9-FCA9C267E55D folder. How to make them visible?
(system details: mail 11.5 (3445.9.1), macbookAir mid-2011, HighSierra)