The Model Browser, sharing a docked tab with the Library Browser, represents the hierarchy of your model.
Note: This panel shows the nested child and parent layers (embedded subsystems) existing in your model.
For example, the folder shown in the screengrab below has a model called 'Electrical car', and one level further below, embedded, you'll find Subsystems named: APU, Battery pack, Electrical motors, Gear reduction, and Rear differential.
Subsystems are displayed, within each layer, alphabetically. When you click the name of each subsystem, its contents are revealed.
To navigate up and down through embedded subsystems, collapse and uncollapse the folders containing the subsystem hierarchies.
The Model Browser is also accessible in the Navigation Bar:
