Maybe it's not about ' how to go backwards : press the key S / check your settings ' but it's about ' how to go backwards : keep the trailer from going AWOL in reverse ' Should be able to skip most of the reversing with trailer, depending on settings.
To help I'll set out the settings needed to achieve the above operation of full automatic, with option to engage sequential and overide when in full automatic mode. Go into SETTINGS - GAMEPLAY. Find Truck Settings. Transmission Type: Real Automatic. Go to KEYS & BUTTONS.
TegCAsV. 412 13 440 310 170 240 106 450 57