Hi
After bricking bavaria 2022 I could finish my trailer with remote controlled sliding curtains, landing legs and parking brake. the mechanism of the sliding curtains works with one PU L motor for each side and two winches at the front and rear of the trailer. Over the winches a cable runs trough the floor of the trailer which pulls the sliding curtains. I'm really happy how the mechanism works :)
But check it yourself in the video:
The instruction for the model can be found here: https://rebrickable.com/mocs/MOC-130914/FT-creations/trailer-with-sliding-curtains/#details
And some renders because I could not make any resonable pictures until now: