Hello,
Those cells should be highlighted in red in the Graphics window with the rest of the mesh being slightly transparent.
To explicitly mark them, if using Watertight Geometry workflow, locate the Outline View tab, expand your mesh object and right click -> Diagnostics tool -> Quality.
You will find a list of various issues or Quality metrics that you can look for/mark. Select one and click Mark. The cells that meet your criteria will be highlighted in the Graphics window.
You are navigating away from the AIS Discovery experience