Add Track to existing controller

Hello,

I'm sure this is fairly easy but I haven't found a way to achieve what I'm asking. In the attached image I have 2 objects, the one with the read circle is what I want, and the blue circle is what I currently have. A previous co-worker that no longer works with the company achieved adding an additional controller to a custom_attribute without a rollout added. Just to make it clean, what I have is:

$vehiclemotion_001.custom_attributes.yaw.controller

what I want to achieve is:

$vehiclemotion_001.custom_attributes.yaw.controller.yaw_animation.controller

How can I add on an additional controller through maxscript? Just incase their are questions about it the Yaw.controller = float_wire() and the Yaw_Animation.controller = Bezier_Float(). Thank you in advance.