The small buttons on the right side of the view title bar control the area displayed in the view and various parameters such as position, orientation, field of view, etc.
To activate them, just click the icons with the left mouse button and drag the mouse, or click inside the view while holding down the appropriate shortcut keys and right mouse button.
Drag the mouse horizontally to move the view from side to side. Drag it vertically to move the view up and down.
Drag the mouse up to enlarge the view. Drag it down to shrink the view.
Click in any view to set a corner, then drag the mouse diagonally to define the area that will be magnified.
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