Grouping lights, controlling multiple switches with one Tile

Updated July 2021.

1. Create a Simulated Switch, it will the the master switch for the group. Alternatively, you may chose to designate one of the existing switches as the master
2. In SmartThings mobile app select Automations, tap +, select Add SmartApp, select Smart Lighting, Create a new Lighting Automation
3. Select all lights that you want to control as a group under "Which devices do you want to control?"
4. Select "Mirror Behaviour" under "What do you want to do?"
5. Select the master switch from the first step under "Mirror which switch"
   

Now, the master switch can be added as a Tile! It will control all lights in the group.