Is there a software design pattern to manage a sequential algorithm with many variations?

I have the following problem. I am looking for a software design pattern (or similar) to help me manage the implementation of a an algorithm with many steps and many variations in each step. It is a sequential (not parallel) algorithm.

It is essentially a directed graph, where the nodes are function/methods and the arrows are calls to those functions/methods. Also, data (objects) is passed and modified between calls.

This is a drawing of the problem

I need a software pattern to help me 1) add and remove nodes and 2) redirect arrows. I looked up in http://www.algorithmforum.com/ but to no avail.

Thanks!