I wonder if it’s a tracking off switch or a panic button? I used to work for a fleet tracking SaaS, and some customers with unionised workforces needed a way to disable tracking, and panic buttons were common too (although less so in Europe).
Around here, such a button in this place would be for the 20 000 lumen extralights. Typically for cars with xenon headlights, like this Opel, the extralights are powered via a relay that takes control signal from a can-bus adapter that extracts the high beam signal, via a manual switch like this.