Bezier Curves Understanding

I am trying to create arrows that go across different bezier curves. Is my understanding correct that I need a curve and just cannot draw an arrow above it as I need a curve to decorate.

I have been able to create curves which work for their lane but I want to start at one curve and go to the other curve using python. I am having difficulty coding this in python. I want to make an iterative function and decorate the curve once I am finished processing the same. I would really appreciate help in this regard.

It’s not really clear from the description what it is you want to do.
Perhaps try posting screen shots or sketches.