Using New Outlook on Windows for personal email, calendar, and contact management
Hi Jane,
Can you still revert to 'old' Outlook? If so, temporarily revert to old Outlook, and re-sort the sub folders A-Z using the right click.
Stay in old Outlook for the day, shut down and then reboot in the morning.
Return to new Outlook and hopefully your sub folders have replicated the folder structure from old Outlook.
I have no idea how or why, nor am I suggesting this is a technical solution, just highlighting that this somehow worked for me.