I see many references online that describe this Root access option in the Developer options for cyanogenmod images like this screenshot from a CyanogenMod13 device

https://www.androidbeat.com/2016/03/how-to-enable-root-access-cyanogenmod-cm/

However I'm tinkering with this older device which may have predated that feature.

Cyanogen OS version
12.1-YOG4PAS2QL

Android version
5.1.1

A related question that could help find the answer is to figure out what would be the appropriate repo in the cyanogen github (https://github.com/CyanogenMod ) to search for the UI that renders this set of options to check when it was first introduced? Basically which repo does the Android GUI go by?