Apple Motion 3 - Manual (Page 238)

238 Chapter 2 Creating and Managing Projects
When you rotate the selection in the Canvas, every object nested within that group
rotates as a single item.
Another example of how you might make use of the group hierarchy can be seen
through the application of filters and behaviors. If you apply a filter to a single layer
within a group, the filter affects only that layer. All other layers within the group remain
unaffected.
Before rotating Left Arm group After rotating Left Arm group
Filter applied to a single layer