Steam controller config can be accessed in steam settings or big picture mode
All you need to do is connecting your PS4 controller to your PC through usb cable.
It would also work if your PC has Bluetooth eliminating the need of wired connection

Simply copy the below url to a steam chat and press it and then apply the settings

Simply use the below url and apply the settings
This configs allow you to toogle big picture easily or even turn off the ps4 controller (if you are using wireless)