Unable to add Shared mailbox on New Outlook

Hello JuliaManansala,

Thank you for posting to Microsoft Community. We are happy to assist you.

If you have permission to the shared mailbox via the added user mailbox added in Outlook, it should show in the left pane under shared with me as shown in the attached screenshot.

However, if you cannot see the shared mailbox still, kindly revert to classic Outlook and close your Outlook and start over the process again. Make sure you migrate your settings from classic Outlook to new as you switch to new Outlook. Migrate your settings to the new Outlook for Windows - Microsoft Support.

If the issue persists, please reach out to new Outlook for Windows support team, as new Outlook is still in preview/production via the in-app feedback site Contact support and provide feedback within the new Outlook for Windows - Microsoft Support

Our Product Development Team are committed to enhancing the customer experience by continually examining suggestions to include in the design and development of future product upgrades based on your suggestions. Hopefully your suggestion will help many users in the future.

Thank you for your time and understanding. For other questions, feel free to add your post in the Microsoft Community team.

Sincerely,

Simbarashe | Microsoft Community Moderator