Working with Animations > Editing Animations > To Insert Tracks and Keys
  
To Insert Tracks and Keys
1. In the Keyframe Editor, select the location for the insertion:
Key—Any point in the timeline
Track—Another track
2. Click Track Tools > Insert Keyframe or Track Tools > Insert Folder. The item is inserted.
You can also insert a track by dragging a part from the Structure Tree to the Keyframe Editor.