I have a 2003 VW Passat & noticed an odd button over the weekend.
It's to the right of the drivers seat between the two doors on that side.
It would probably usually be hidden by the seatbelt.
It's at the same kind of level as the seat adjuster (to move the back of the seat forward or back).
I can't see anything in the manual & it doesn't seem to do anything when pressed.
Its to deactivate the interior monitoring system. With it deactivated, you can arm the alarm and still leave a dog, child whatever inside.
To use, press after removing the ignition key, a light should illuminate in the button then if you lock the car within 30 seconds interior sensors are off.
However, it may not be operational. Depends on the specifications of the car