Manage Assemblies floating windows allow you to quickly find and isolate Primary and Secondary Assemblies.
Difference of Primary and Secondary Assemblies: Primary Assembly has drawings, Secondary doesn't.
Select any assembly and execute Show Primary Assembly command. Primary Assembly will be found and its View will be zoomed in.
Select any assembly and execute Show Primary & Secondary Assemblies command. All assemblies of the same type will be selected and zoomed in the view.
Select any Assembly and execute Isolate Selected Assemblies command. Everything except selected Assemblies will be hidden.
Unhide Assemblies will reveal all hidden elements in the view.