User Configuration > Administrative Templates > Microsoft Project 2016 > Project Options > View > Show
User
HKCU\software\policies\microsoft\office\16.0\ms project\options\view
Specifies whether separate windows are opened and displayed as separate buttons on the Windows taskbar for every open project. If you enable this setting, a new window is displayed in the taskbar for each open project. If you disable or do not configure this setting, the user's default setting is used.