Yes, you (usually) want to transform your trajectories to correspond to your robot’s current position. WPILIB has a function that does this for you:
Pose2d bOrigin = m_drivetrain.getPose();
Trajectory bTrajectory = aTrajectory.relativeTo(bOrigin);
Note that this assumes your Trajectory is already based from the origin. If it starts from another point you may need to subtract the initial pose from the Trajectory, or simply move it relativeTo (0, 0, 0).
Also, you might want to initialize your robot’s pose at startup to know where it is positioned on the field. I call m_drivetrain.resetOdometry() with the intended starting pose so that the path following knows where you are, initially. This will make the robot icon appear in the correct spot in the Field2D visualizer, in your case ( x=7.5, y=-22.5) and (heading=0).