Hi @Marc L ,
According to my research, this feature is not available in New Outlook preview. The new Outlook is not yet complete and some options may not be available or work as expected. You can switch back to the classic Outlook at any time by clicking the toggle button in the top right corner of the window.
Please kindly understand that many functions of our current products are designed and upgraded according to customer feedback. Someone has already submitted this feedback in the dedicated feedback portal, you can also vote for the post via this link: https://feedbackportal.microsoft.com/feedback/idea/55f3aae6-72b9-ee11-92bd-6045bdaf7237
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