I have several routed cables that have additional parts on them besides the end connectors. I cant figure out how to add these parts to the flattened harness? Our approach is to have a routed cables assembly, then use a manufacturing harness to flatten the harness for the final length. In many cases the flatted assembly is better for the manufacturing drawing. I cant figure out how to add these additional components.
The way I usually add backshells and other stuff is to route the harness through a location on a feature of the add-on (csys, axis, other) then use the Attach to Harness command to actually add the component to the harness.
When you flatten, you may have to flatten the backshell then the connector manually to get them to lay correctly particularly if the harness is not straight from the backshell location to the connector location. I usually end up having to add bends and rotates to get them to line up reasonably well.
Another option is to make the backshell part of the connector, either as a single part which would require some juggling to get the BOM to work out correctly or as an assembly (don't know how BOM would work with that option).
In Cabling mode in the assembly, there is a command in the ribbon for Attach to Harn (IIRC). It connects the backshell or other accessories to a location point on the harness. Then in Pro/HARNESS when you're flattening the assembly you'll be able to add those components.