You'll find this under the option Additional buttons under settings, it has always been there since CM13.
Since it's unified, firmware package must be updated by you when they change kernel code to newer which requires newer firmwares. Else those with the none T model would brick their phones when installing this ROM. ?
#include <std_disclaimer.h> /* * Your warranty is now void. * * We are not responsible for bricked devices, dead SD cards, * thermonuclear war, or you getting fired because the alarm app failed. Please * do some research if you have any concerns about features included in this ROM * before flashing it! YOU are choosing to make these modifications, and if * you point the finger at us for messing up your device, we will laugh at you. * */