Hide or Show all Tracks Simultaneously:
- Press and hold down the Alt key on your keyboard.
- Left click on the Show/Hide icon of any track in the Track list window.
NOTE: The Track List window is located at the top left of the Pro Tools Edit and Mix windows. The track Show/Hide icon is the black dot to the left of a track name in the Tracks window. I've drawn a red square around the Show/Hide icon in the image below.