In direct mode the the manual rudder trim cancel switch is inoperative.
Below are extracts from the 777 Familiarisation manual
A rudder trim selector, on the aisle
stand, supplies trim signals to the
ACEs. The rudder trim actuator
moves the rudder pedals when
commanded by the ACEs. Two
rudder trim rates are available. A
rudder trim indicator, also on the
aisle stand, shows the rudder trim
position.
A manual trim cancel switch, on the
aisle stand, sends a signal to the
ACEs to command the trim to zero.
A switch on the P5 overhead panel
permits the pilots to disable the thrust
asymmetry compensation function.
A rudder tab hinges on the rudder.
The tab moves mechanically with the
rudder to increase its effect.