Relevant to Blender 2.33
This section describes the general functions of the mouse and keyboard, both of which work uniformly throughout the Blender interface. Each Blender window also offers a number of specific options. These options are described in the following sections.
Each time you place the mouse cursor over the edge of a Blender window, the mouse cursor changes shape. When this happens, the following mouse keys are activated:
LMB (hold-move). Drag the window edge horizontally or vertically. The window edge always moves in increments of 4 pixels, making it relatively easy to move two window edges so that they are precisely adjacent to each other, thus joining them.
MMB or RMB. A PopupMenu prompts for Split Area or Join Areas or No Header.
Choosing Split Area, Blender splits the active window in two and allows you to indicate the exact split point. To cancel the split press ESC. Split creates an exact copy of the original window.
Choosing Join Areas, Windows with a shared edge are joined if possible. The active Window remains.
If there is no Header in the Window, the PopupMenu contains the item Add Header rather than No Header.
The Window Header. Blender window headers offer the following extra options in combination with mouse keys:
LMB on the header. The entire Blender window pops to the foreground.
CTRL LMB on the header. The entire Blender window pops to the background.
MMB (hold-move) on the header. If the Blender window is not wide enough to display the entire header, the MMB key can be used to horizontally shift the header.
RMB on the header. A PopupMenu appears asking for Top, Bottom or No Header. That way the header can be moved to the top or the bottom of the Blender window or can be hidden.
You can add a header to a Window by pressing the middle Mouse over an edge of a headerless Window.