What is a User Step
User steps are tasks that the users have to do to reach their goals.
During the story mapping session, you should collect all the interactions that belong to the User Goal.
User steps are organized into the second row on the story map, and similarly to user goals, we recommend ordering them into the narrative flow. So you can easily retell the user journey by reading steps from left to right.
User goals and user steps make the Product Backbone.
How to order parallel or optional goals and steps?
Rethink the goal — it might be cut into two goals. E.g. "Buy product" can be split into "Buy with credit card" and "Buy with POD"
You can keep parallel steps under the goal and mark them with personas, labels, or card colors
What to do when a backbone becomes too wide?
If you're managing a large product you can split the story map by product components or product lines
If you want to keep everything on the same story map, you can collapse goals (if you want to focus on other parts of the journey), or you can hide goals as well (if that part is currently out of your scope)