If too many objects are visible in a view, select the objects you want to view and use the Home > View > More > Show Selection Only command to refresh the view so that only the selected items are visible in the window. If you change the view type in the window, say from a plan view to a 3D view, the originally selected items continue to be the only ones visible.
Use the Home > View > More > Show All command to restore all objects to the view.
Note: Right clicking anywhere in an active window will display a drop-down menu of commands, including the Show Selection Only command. Clicking that command is the same as using the Home > View > More > Show Selection Only command. Thus, select objects before right clicking and selecting the Show Selection Only command from the resulting drop-down menu.