The window associated with a composition resembles the Main Timeline window in the way it is operated. However, its purpose is quite different. Unlike the main timeline and auxiliary timelines, its output doesn’t appear directly on stage. Instead, you use the composition from another timeline similar to playing a video clip. See Compositions for details.
Create a composition by choosing “Add Composition” on the Media menu. A new composition item appears in the Media window. To open the timeline window of a composition, double-click its name in the Media window. Use the “Timeline Settings” command on the Timeline menu to change the name or other properties of a composition (such as its reference frame).
NOTE: When opening a composition, its preview will temporarily replace the normal content of the Stage window. This doesn’t affect the image shown by any display computers. Close the composition to restore the Stage window.