How can the following user notification by resolved:
"Conduit has a Stop control structure, but this is not supported next to the connected outfall element."
The program does not allow conduits with stop contol structures to connect directly to outfall. The steps taken to work around this issue may vary depending on what is being modeled. However, some additional node and link must be added between the outfall and the conduit with the stop control structure.
One possible setup can be seen in the screenshot above:
This case could work if the stop control structure is modeling the point where conduit flow goes into a channel. You can also add another manhole and a large diameter pipe that connects the conduit with the stop control structure to your outfall.
Once you have some additional link, be it a conduit or a channel, you should be able to add the stop control structure.
Conduit start/stop control structures