As I read the system diagram, you won't be able to move the THS inflight without hydraulic pressure.
The mechanical link interacts with the hydraulic motor (jack?) to move the THS up or down via the trim wheel commands.
Hydraulic motors from blue and/or yellow hydraulic systems power the jack.
If the electrical controls are still working (as one would expcet in Alternate Law) an electric motor tells the hydraulic motor/jack which way to move, and how much. (Notation a few posts up on damping appreciated, I finally "got" how that works in normal operations).
If I misunderstand what moves the THS, I'd appreciate any corrections so I can annotate my slides.