Heartline Generator

hey, I just downloaded Busters Heartline Generator and its totally new to me.
Im building a design and I cant get the rear car of the train to be smoother.
I do use the node smoother as I go along but thinking on using the heartline gen as I build.
What my main question is , can someone tell me if I can use the Generator on segments as I continue to build the track or do I have to first finnish the track to use it?

For ease of use, I would just wait until you are done the entire track to use it.