TrailerAssist is a small tool to make reversing with a trailer easier. You activate it with the following keys:
F11: Navigation with compass; TrailerAssist attempts to move the trailer in the indicated direction
F12: Navigation angle between tractor and trailer; TrailerAssist tries reach the displayed angle between tractor and trailer
A: Turn left
D: Turn right
Ctrl T: Activate TrailerAssist permanently.
You can see that TrailerAssist is activated when grade numbers with yellow font appear at the top of the screen. Although TrailerAssist is permanently switched on, it will only be active when driving backwards.