Select objects underneath
Sometimes there are duplicate objects below your most top object. There should be a command or feature that lets you see/ select duplicate geometries right below your top shapes. 
This is most evident on shapes with the same dimension.
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      Ana, there is an existing option that might help you with selecting stuff underneath the currently selected objects. 
 Go to Preferences > Selection & Anchor Display and enable 'Control Click to Select Objects Behind' (not sure the names is the same on MacOS)
 So, now, after you click an Object with Cmd/Ctrl once, the cursor gets a small '<' next to it, indicating you are now in 'Select Behind' mode. You can click again and more to continue selecting objects behind.
 Does it help you in any way?
 
          