adding shortcut to on off flash light to volume button

[Sandeepganji]

Flash light short cut 

[Sidhabhi]

You can use lockscreen shortcuts(bottom corners)
or
install one hand operation+(samsung official app)

http://apps.samsung.com/appquery/appDetail.as?appId=com.samsung.android.sidegesturepad

[imankur]

Try it👇

[Ehsank]

always mention your device name
use sidekey as flashlight option