CitySample - Enable - Render custom depth pass

I’m working with the CITYSAMPLE project, and I need to enable CustomDepth Pass (under Details panel > Rendering > Advanced) for all objects.

However, I haven’t even been able to enable it for a single object. I tried selecting a building, but the option appears read-only and disabled.

I’m not sure what I’m doing wrong.

Any advice would be greatly appreciated!

Thank you.