When elements are overlapped in a schematic or system diagram, use Shift + Ctrl + click to cycle through which items will be selected.
For example, see the schematic below with two microstrip models that are partially overlapped.
If you clicked in the region where the two models overlap, the top model in this case would be selected.
However, if you hold down Shift + Ctrl and then click in the same region, the first click would select the same model. The second click would select the bottom model. This mode will cycle through all models that are overlapped.
Remember that if you are in a dense area of your design and it isn't obvious which model is selected, you can always view information on the status bar, along the bottom of the AWR Design Environment. In this example, after the second mouse click, the status bar shows that MLIN.TL2 is selected.