Sony DCR-TRV39 - Manual (Page 220)

Selecting multiple thumbnails (scattered)
Windows:
Press and hold the [Ctrl] key on the keyboard and click all thumbnails.
Macintosh:
Press and hold the [Command] key on the keyboard and click all thumbnails.
Select entire thumbnails
Windows:
Press and hold the [Ctrl] key and press [A] key on the keyboard.
Macintosh:
Press and hold the [Command] key and press [A] key on the keyboard.
Switching thumbnails
You can switch between thumbnails by clicking the [decrease] and [increase]
buttons.
Sorting/Changing thumbnail order
There are two ways to sort/change thumbnail order as below: