Trailer Assist

Trailer Assist makes reversing with a trailer easier. You activate it with the following keys:

Alt+T: Toggle Trailer Assist permanently on/off.
Shift+T: Hold to activate rotation mode (compass direction).
Ctrl+T: Hold to activate tool angle mode (angle between tractor and trailer).

You can see that Trailer Assist is activated when yellow degree numbers appear at the top of the screen. Trailer Assist will only be active when driving backwards.