Using Classic Outlook on Windows for personal email, calendar, and contact management
Hello FransLab232,
Thank you for posting on Microsoft Community!
For this issue, I also had a test from my side, and the result is as same as that of yours-the dropdown menu is unavailable now. It's a design limitation of New Outlook currently. Please comprehend that the New Outlook is a beta version, and the product group are collecting feedback from customers to develop the product better. We really appreciate you bringing this to our attention. You may Contact support and provide feedback within the new Outlook for Windows.
As a workaround, you can switch back whenever you want, just switch the toggle off in the new Outlook and it will automatically open the classic version.
If you need further assistance, feel free to reply! We will continue to support!