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: Door adjustment
1. Measure the gap and height between the front or rear door and the body.
2. If not as specified, loosen the front or rear door hinge installation
bolts or the door lock striker installation screws, and reposition the door.
Clearance
a: 2.5-4.5 mm {0.10-0.18 in}
b: -0.8-1.2 mm {-0.03-0.0 ...
Mazda 6 Owners Manual: Instrument cluster removal/installation
Caution
When replacing the instrument cluster, the configuration procedure must be
performed before removing the instrument cluster. If the configuration procedure
is not performed before removing the instrument cluster, it is possible that the
instrument cluster will not operate normally. ...