from the Help
Automatic Mode is the default mode. It ensures that all items that can be animated located in the various Managers, such as objects, tags, materials, render settings, etc. are automatically displayed in the Timeline.
If this mode is not active, the Individual Mode will be in effect. Items must then be placed into the Objects Area from the corresponding Manager per drag & drop. Only these items will then be shown. This means that the first time you switch to Individual Mode the Timeline will be empty until something is dragged into the Objects Area. If you press the Shift key while dragging and dropping items into the Objects Area all Child objects will be placed there as well.