To use the armrest, pull it forward from the seatback.
Kia Niro 2017 (DE HEV) Service Manual: Inside Rear View Mirror Components and components location
Component Location
1. Inside rear view mirror
...
Kia Niro (DE HEV) Owners Manual: Power window lock button
The driver can disable the power window switches on the rear passengers’ doors
by pressing the power window lock switch to the lock position (pressed).
When the power window lock switch is pressed :
The driver’s master control can operate the front passenger’s power window
and the ...