pg 286, ch.5-113, of the manual has the sliding armrest 'pic':
Sliding console
2C_SlidingArmrest
To slide the console (2)
forward/backward, pressing the handle
(1) and pull or push the console to the
desired position.
Check if the console box makes a ‘click’
sound, after moving the center console
box.
NOTICE
Use of excessive force to the console box
may damage the sliding rail or the control
lever.