The rear armrest in the center of the rear seatback can be used (no occupant in the center seat) or placed upright.

WARNING
Never put your hands and fingers around the moving parts of the seat and armrest:
Putting your hands and fingers around the moving parts of the seat and armrest is dangerous as they could get injured.
Split Folding
Head RestraintsMazda 6 Owners Manual: Blind Spot Monitoring (BSM) (Some models)
The Blind Spot Monitoring (BSM) is designed to assist the driver in checking
the area to the rear of the vehicle on both sides during lane changes by notifying
the driver of the presence of vehicles approaching from the rear in an adjacent
lane.
The Blind Spot Monitoring (BSM) detects vehicle ...
Mazda 6 Owners Manual: Power brake unit removal/installation
1. Remove the master cylinder. (See MASTER CYLINDER REMOVAL/INSTALLATION.)
2. Remove the wiper arm. (See WINDSHIELD WIPER ARM AND BLADE
REMOVAL/INSTALLATION.)
3. Remove the cowl grille. (See COWL GRILLE REMOVAL/INSTALLATION.)
4. Remove the wiper motor. (See WINDSHIELD WIPER MOTOR REMOVAL/INSTAL ...