Hi Yossi. I am an independent advisor, trying to help other users in the Community with my experience in Microsoft products. Please note that I am a user like you and don't work directly for Microsoft.
I am sorry you are having trouble with Outlook not working as it should. I understand this can be pretty frustrating. I apologize for the inconvenience. Let me try to help.
Disclaimer: This is a public user-to-user community forum. None of us here work for Microsoft and it is beyond our capability to assist directly with the account or login-related issues. Just so there is no misunderstanding, this is a public user-to-user support forum. We're users just like you helping other users. We do not work for Microsoft and have no access to any user account so there is nothing we can do or check from within the forum. We have no input on Microsoft's policies, procedures, or design decisions. Microsoft Support personnel do not staff this forum.
The inability to locate the "Open in new window" option is not exclusive to you as many other users have complained about the same thing; myself included. It would appear that function was indeed removed recently.
Please Keep in mind that the New Outlook is still evolving, and more features are being added over time.
What you can do is providing feedback directly to Microsoft through the feedback portal https://feedbackportal.microsoft.com/feedback so that they can reverse this decision and include the feature to upcoming versions of the application.
I hope this helps
Regards
Femi