Editing : Edit Modes and Tools : Zoomer Tool : Continuous Zoom with the Zoomer Tool

Continuous Zoom with the Zoomer Tool
Use the Zoomer tool to zoom in or out continuously.
To use continuous zoom on one track or a group of tracks:
1 Select the Zoomer tool.
2 Hold the Start key (Windows) or Control (Mac) and do one of the following:
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For horizontal zoom, all tracks zoom together. Tracks will zoom in or out centered horizontally on the location where you click.