In brief
In the variant described, the driver selects the desired trajectory.
Useful to know
Bosch's trailer tow assist supports rearward movement with a trailer. A rear camera determines its position, and the driver selects the desired direction via an interface; the system makes the steering adjustments. [1]
In the principle described, the driver continues to control the speed with the pedals. This is an essential distinction when compared to a fully automated parking maneuver. It also keeps track of the actual space around the trailer, which may be wider than the vehicle. Do not assume that one light trailer function is automatically suitable for every type of trailer and every load.
Sources
For further detail and to check the information: