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: Limitations to SRS Air Bag
In severe collisions such as those described previously in "SRS Air Bag Deployment
Criteria", the applicable SRS air bag equipment will deploy. However, in some accidents,
the equipment may not deploy depending on the type of collision and its severity.
Limitations to front/near front collision ...
Mazda 6 Owners Manual: Cruise actuator removal/installation
1. Disconnect the negative battery cable.
2. Remove in the order indicated in the table.
3. Install in the reverse order of removal.
Cover Removal Note
Unclamp the clips of the heater hoses at the front of the cover.
...