Studio Main Panel opening as new window

How do I pin the Main Panel ( where the main.xaml ) and adjust the size so that i stays in foreground on the designer. Whenever I adjust size it opens as a new window and I no longer see it pinned in the designer. I tried reinstalling Studio and that didn’t solve the problem. So when I open a project, the main panel opens in full screen but i am not size and make it stay between the activities panel and properties panel.

Thanks