Apple Motion 3 - Manual (Page 355)

Chapter 4 Using the Timeline 355
Trimming Objects in the Group Track
Trimming the edges of the group bar automatically trims the edges of the objects
within the group. If there is only one object, trimming the group bar simply trims that
object. If there is more than one object lined up with the edge of the group, trimming
the group automatically trims all of those objects.
You cannot trim the individual object tracks within the body of the group track.
Disconnecting the Group Track from Its Contents
You can modify the group bar to be longer or shorter than the contents of the group.
For example, you might shorten a group bar to hide a section of the objects within it.
Objects that extend beyond the boundaries of the group bar (the thin blue bar at the
top of the group track) are not displayed in the Canvas.
To change the length of the group independently from the objects within it:
m Press Command, then drag the edge of the group track.
Only the thin blue layer bar is trimmed.
Note: Once you manually change the length of the group bar, it is no longer
automatically updated as you add or modify the objects within it. To restore automatic
updating, realign the group bar with the right edge of the last clip in the group.
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