Volvo 2008 V70 Owner's Manual page 39

With the booster cushion in the stage 1 position, press the button (see the arrow in illustration 1).
Lift the front edge of the booster cushion and press it rearward toward the backrest to lock it in position.
47
01 Safety
Integrated booster cushion
Stowing the two-stage integrated booster cushion
The booster cushion can be folded down completely (stowed) from either the stage 1 or stage 2 positions.