Debug Dedicated Server in Unreal

First follow this tutorial:

https://docs.unrealengine.com/en-US/InteractiveExperiences/Networking/HowTo/DedicatedServers/index.html

Then, open Visual Studio and Right Click the project, choose Properties, go to the Debugging section — there is a box for “Command Arguments”. add “/Game/Maps/YourMap -log -port=9999 -server”

Press F5 or right-click debug on your project’s folder.

You are good to go!