Editing : Edit Modes and Tools : Zoom Preset Buttons

Zoom Preset Buttons
Pro Tools lets you save up to five horizontal Edit window Zoom presets, which can be recalled by typing a number or by clicking a Zoom Preset button.
To store a view as a Zoom preset:
1 Use the Zoomer tool to configure the Track View.
2 Click and hold one of the Zoom Preset buttons (1–5) and choose Save Zoom Preset from the Zoom Preset pop-up menu. The preset button flashes momentarily, and any previously stored Zoom preset at that number is replaced.
 
To recall a saved Zoom preset, do one of the following:
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– or – 
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Click and hold the Zoom Preset button and choose Recall Zoom Preset from the Zoom Preset pop-up menu.