Currently, The story map functionality was designed for use cases where a step includes 1 or more epics, and stories would be displayed under the respective epic to show the parent/child relationship.
However, since it is called a user story map, it would be super nice if we can have steps and every step can have 1 or more user stories (Vs the EPICs) and just delete the EPIC relationship in the map itself. The stories can be tied to EPICs but, it would be great to see every step and what stories are lined up to those steps.