Editing : Making Selections : Linking or Unlinking Track and Edit Selections

Linking or Unlinking Track and Edit Selections
Pro Tools lets you link or unlink Track selection with Edit selections.
When Track and Edit selections are linked, you can make a selection within a track or across multiple tracks for editing and each associated track is selected (track names automatically highlight). This lets you quickly apply track-level commands (such as Track View toggle, change track heights) and have the command apply to all tracks you are working on.
When Track and Edit selections are unlinked, making an Edit selection does not automatically select all associated tracks.
To link or unlink Track and Edit selection, do one of the following:
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Select or deselect Options > Link Track and Edit Selection.
– or – 
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In the upper left of the Edit window, under the Edit tools, click the Link Track and Edit Selection button so it becomes highlighted (selected) or un-highlighted (not selected).