Hello @delta,
Accordingly to the Works Library - Tasks Reference Guide
WriteSignal
A WriteSignal task allows you to set the value of a signal in a static component. Signal type must be either Boolean, integer, real, or string. You cannot use a WriteSignal task with IO ports of a robot but can refer to signals connected to those ports.
As explained in the last line, if you add a boolean signal to the robot, then you could connect the WorkProcess to that signal.