Hide Property Timelines

To hide property timelines:

To hide an individual object's property timelines, click the name of the object whose properties you want to hide.
To hide all the property timelines of an object and its children, hold down Opt/Alt while you click on the name of the parent object.
To hide all property timelines in the Hierarchy List Area, select Collapse All Timelines from the menu to the right of the Preview Area.

When all the object timelines are hidden, the only thing displayed in the Hierarchy Area is the hierarchical structure of your scene.