Selecting using the mouse
                                          

To make a new selection: 
1. Hold down the shift key.
2. Click in the play bar away from the thumb.
    The thumb jumps to the new point.
3. Drag to a different point.
    The selection begins following the thumb.
4. Release the shift key or the mouse to stop.

To extend a selection you’ve started: 
1. Hold down the shift key.
2. Click on the thumb drag to a new point.
    The selection begins following the thumb.
3. Release the shift key or the mouse to stop.