MacBook Pro – What is the Green Symbol on the Touch Bar

You can use my script until Apple adds a preference for the Touch Bar.

It simulates keyboard activity by sending the command for the fn-key every 60 seconds. You should not notice it while typing. Keep in mind, however, that this will prevent display sleep / system sleep as well.

Copy and paste the following code into the "Script Editor" application on your MacBook Pro with Touch Bar:

(*
1. Save as an Application: Script Editor > File > Export… > File Format: Application
2. Check "Stay open after run handler"
3. Run the app or add it to your login items: System Preferences > Users & Groups > User > Login Items > Press the "+" button

# http://apple.stackexchange.com/questions/269174/disable-the-sleep-function-of-the-macbook-touch-bar
*)

on idle
    tell application "System Events" to keystroke (key code 63) -- press fn key
    delay 60
end idle

Please let us know if this solves your issue.

It seems to be linked to the simulator in Xcode.

When pressed this expands into some debugging shortcuts as shown in this screenshot:

You can also see this icon on 9to5 macs article about the touchbar. 9to5mac link