Have separate windows
In the Windows version of Outlook, you can have a separate window for Mail, Calendar, Contacts, etc. In Outlook for Mac, all these functions are within the same window. I suggest you provide this capability to the Mac version. This will prevent users from having to switch back and forth in the same window for data that may be needed for other parts of the application.
Until recently, you could have two "Main Windows" open (File > New > Main Window) and make one window be Mail and the other Calendar, but the last couple of versions on the "Slow" development track have broken this. The second window will open, but you lose function and/or display information.
Olivier Biot commented
This already exists. In Outlook app menu, choose File > New > Main window.
Alessio Roic commented
This is already supported. In the menu go to File/New/Main Window. Then you can change it to be Calendar/COntacts/Notes.