Try setting Open Windows as Tabs.
I couldn't find where to change this in Preferences, but I did change the Display quality to high and now the window is in the right place. Very weird!! Hopefully it will stay this way.
It is actually not a preference.
Method 1: Go to menu WINDOWS->ARRANGE
Method 2: Move the window with the mouse. When the window edges touch the tool bar edges, the window should be framed by a blue frame. Let go and it will be tabbed.
Opening windows as tabs actually IS a preference, in the Interface section. Mac users may need to activate the Application Frame as well (as a Windows user I don't have an option).