Adding a shared mailbox with it's own Outlook profile

To add a second, fully independent profile for an account (either a delegated user mailbox or shared mailbox), do the following

1. Open Control Panel
2. Open Mail
3. Click Show Profiles
4. Click Add
5. Give the profile a name
6. Choose Manual setup or additional server types
7. Under Microsoft 365, enter the name of the mailbox you'd like to add
8. Click Next
9. Click Finish

If you want to set a default profile, choose one on the Mail screen: