Q:

No splitter widget in new separate window

I am new to Blender and I am trying to find my way through its interface. I want to have several windows (I mean OS windows, not Blender windows). So I create a separate window by dragging splitter widget while holding Shift.
The problem is there are no splitter widgets in the newly created OS window. So I can't have multiple blender windows in it. The new window does not have a Layout type drop down menu either. So how do I add new Blender windows in a new OS window? (Sorry if I'm using the wrong terms, but hopefully its clear what I am trying to achieve).

A:

The reason you cannot split the windows is because you have one of your part of the User Interface maximized. 

Once you go out of this maximization via pressing the "Back to previous" in the info header or by pressing Shift Space you can change your UI and create new windows.
Some other shortcuts to manipulate the User Interface.

Shift+Space, Ctrl+Up,Ctrl Down: Maximize Window under mouse
Ctrl+Left, Ctrl+Right: go to previous/next Layout

A:

This is because you toggled your window full screen.
You can click the button "Back to previous" at the top, or hit CTRL + UP arrow (or CTRL + DOWN arrow, or again SHIFT + Space bar) to toggle the window full screen / normal.
The "split view" widgets are only present when not in full screen.

