The "servertravel" command doesn't function when running ShooterGame in Editor.
A warning will show up in the Output Log:
LogWorld:Warning: UWorld::ServerTravel: Seamless travel currently NOT supported in single process PIE.
This warning will appear whether you're using single process or not.
However, when running the ShooterGame with -game with a server and client the servertravel command works fine, but the "setall" command is not recognized.
The server and the client both travel to the Sanctuary map.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-20182 in the post.