Final answer:
The park brake warning light is the component in the Beta-Freightliner cab that indicates the vehicle cannot be moved when the lift platform is not fully set in the DOWN position.
Step-by-step explanation:
The component in the Beta-Freightliner cab that illuminates and indicates the vehicle cannot be moved whenever the lift platform is not fully set in the DOWN position is the park brake warning light.
This light is designed to alert the driver that the lift platform is not properly lowered, preventing the vehicle from being moved. It serves as a safety feature to prevent accidents while the platform is still elevated.