Catch basins have the following flow types that can be added: additional subsurface flow (cfs), known flow (cfs), additional carryover flow (cfs), external CA (acres), and external Tc (min). Manholes only have the option of known flow. Known flows can be overwritten or replace other known flows downstream which could create a lower total system flow if not used properly. If you have to run more than one design storm, you would have to manually change the known flow for each storm which is not feasible. I would like external CA (acres) and external Tc (min) to be added as a drainage utility property for manholes.