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: Trunk side trim removal/installation
4SD
1. Remove the trunk end trim.
2. Remove the fasteners, then remove the trunk side trim.
3. Install in the reverse order of removal.
5HB
1. Remove the trunk end trim.
2. Remove the trunk side upper trim.
3. Remove the cargo hooks.
4. Remove the fasteners.
5. Pull the trunk side trim ...
Mazda 6 Owners Manual: Height Adjustment
Adjust the head restraint so that the center is even with the top of the passenger's
ears.
To raise a head restraint, pull it up to the desired position.
To lower the head restraint, press the stopcatch release, then push the head
restraint down.
Front outboard seat
Rear outboard seat
...