About group tracks
You can edit in the group track, even if the group is collapsed and its nested objects are not visible in the Timeline track area.
Group tracks contain two colored bars. The narrow, dark-blue upper bar edits all objects in the group as a single unit. It’s labeled with the name of the group (“Group” by default). The lower group bar—taller and a lighter shade of blue—edits individual objects in the group. The lower group bar displays information about the names of individual objects in the group, as well as the number of objects that overlap in composited areas of the Timeline.
Motion lets you move objects in the Timeline via the group track. Depending on where you drag in the group track, you can move all objects, individual objects, or just those objects that overlap in time (composited objects).
Trimming the edges of the upper group bar trims the edges of the objects in the group. If there’s only one object, trimming the upper group bar trims that object. If there’s more than one object lined up with the edge of the group, trimming the group trims all those objects.
You cannot trim overlapping objects via the group track.
You can modify the upper group bar to be longer or shorter than the contents of the group (the lower group bar). For example, you might shorten the upper group bar to hide a section of the objects in it. Objects that extend beyond the ends of the upper group bar are not displayed in the Canvas.
In addition to moving and trimming, you can slip video layers in the group track. Any portion of the lower group bar that contains only one video layer can be slipped in this manner. Areas where more than one layer overlap can be slipped by Control-clicking the group bar and choosing a video layer from the shortcut menu. For more information, see Edit in the group track.