Hi @Alain Oser ,
Currently, templates in the classic version are not supported in New Outlook for Windows. And the development team is working to support this feature in the feature releases of New Outlook for Windows.
As a workaround, you can use add-ins to Create or edit email templates in New Outlook for Windows.
Besides, you can switch back whenever you want, just switch the toggle off in the new Outlook and it will automatically open the classic version. Then you can Create an email message template just like you used to.
You can also access the link below to get updates for the New Outlook for Windows:
Getting started with the new Outlook for Windows
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.