Binding to variables and methods within the hierarchy
When you have the Configure window open, it will show the variables, methods and component actions available for synchronization for your currently selected GameObject.
If the Prefab that you are configuring has a hierarchy, you can synchronize variables, methods and component actions for any of the child GameObjects within the hierarchy.
To do so, open the Prefab in Prefab Mode by clicking the Open Prefab option in the inspector. This will allow you to select any of the GameObjects that belong to the hierarchy, the Configure window will be updated automatically, showing you everything that is available to be synchronized.
Configuration window showing Open in Prefab Mode.
A Prefab Stage showing Player, and configuring a child in the hierarchy.
To edit child GameObjects, make sure you click on them in the hierarchy. A Configuration window will pop up.