swmm is more of an analysis engine, not design. Therefore the more common workflow is to design using HEC-22 and then do a dynamic swmm analysis for validation of the design. In the OpenRoads world the workflow would go as follows:
- Layout the drainage system with Subsurface Utility Design and Analysis.
- Design the systems using Subsurface Utility Design and Analysis, which is in fact StormCAD.
- Still inside Subsurface Utility Design and Analysis: when you are satisfied with the drainage design for peak flow, go into the top menu and activate one of your Civil Storm licenses
- Compute a swmm analysis of the drainage network to validate your peak flow design.
- With the Civil Storm license still active, design ponds as necessary.
All the above is done in the same product, same installation, same dataset. Plus, sounds like you might now have some extra licenses which you could swap for something else using portfolio balancing.