See also:

Cup holder in the rear seat armrest
Do not sit on or support your body weight on the rear seat armrest when it is folded down, as you could otherwise damage it. Close the cup holder before folding the rear seat armrest up. ...

Making adjustments in 5 mph (Canada:10 km/h) increments
► Briefly press the cruise control lever beyond the pressure point, up 1 for a higher speed or down 2 for a lower speed. The last speed stored is increased or reduced. ...

Roadside Assistance button
Open the stowage compartment under the armrest. Press and hold Roadside Assistance button 1 for more than two seconds. This initiates a call to the Mercedes-Benz Customer Assistance Center ...