The trajectory is published on a topic.
Every module publishes a new trajectory after it’s done working with the trajectory.
So for example if you modify the trajectory, the output of this operation will be the full trajectory (ram_msgs::AdditiveManufacturingTrajectory type) being published on the ram/trajectory topic.
All you need to do is create a subscriber that listens to the trajectory topic. Each time a new trajectory is generated, modified etc… you’ll get a new message containing the latest trajectory.