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: Locking, Unlocking the Doors
NOTE
The system may not operate if you are too close to the windows or door
handles.
If the key is left in the following areas and you leave the vehicle,
the doors may be locked depending on the radio wave conditions even if the key
is left in the vehicle.
Around the dashboard
...
Mazda 6 Owners Manual: Transaxle range (tr) switch inspection
Operating Inspection
1. Verify that the starter operates only when the ignition switch is at the
START position with the selector lever in P or N position.
If not as specified, adjust the TR switch.
2. Verify that the back-up lights illuminate when shifted to R position with
the ignition ...