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: Moonroof (Some models)
The moonroof can be opened or closed electrically only when the ignition is switched
ON.
WARNING
Do not let passengers stand up or extend part of the body through the open
moonroof while the vehicle is moving: Extending the head, arms, or other parts
of the body through the moonroof is dan ...
Mazda 6 Owners Manual: Rear window glass installation
Caution
To prevent the sealant from cracking or the glass from being
pushed out by air pressure if a door is closed, open all of the windows and
leave them open until the sealant has hardened.
1. Cut away the old sealant using a razor so that 1-2 mm {0.04-0.07 in}
thickness of sealant ...