Mercedes-Benz GLC : Through-loading feature in the rear bench seat (EASY-PACK Quickfold) / Adjusting the angle of the rear seat backrests (cargo position)
To enlarge the cargo compartment, you can
adjust the seat backrests so that they are ten
degrees steeper (cargo position).

Fold the seat backrest
forwards.
Move bracket
in the direction of the
arrow.
Push seat backrest
back to bracket
until the backrest engages.
Requirements:
The left and center seat backrests are
engaged and joined together.
You can lock the center seat backrest release
catch if you want to secure the cargo compartment
against unauthorized access...
Other information:
..
If the left-hand rear seat backrest is folded down
and back up again, it may not be possible to pull
out the rear passenger compartment center seat
belt. The seat belt must be released.
Pull the seat belt out approximately 1 in (25 mm) at the seat belt outlet on the seat backrest and then release it again...