When you add a manager, apps like ‎Teams‎ and ‎Outlook‎ will be able to show organizational charts to users. Note that each user can only have one manager at a time. 
  1. Navigate to the Active Users page in the Microsoft 365 Admin Center: https://admin.microsoft.com/AdminPortal/Home#/users
  2. Select the User by name
  3. Click Add manager under Manager:
  4. Choose manager by entering Name or Email address:
  5. Click Save Changes:
  6. Done! You will see this green banner when successfully added: