Using SB makes it easy to debug custom plugins. To do so, publish the plugin with Debug configuration:
Then, copy the output to the Plugins folder, and run the server.
Finally, make a break point, and attach to the process by selecting Debug -> Attach to process… -> Check the Show processes from all users checkbox, and find the dotnet process.
Visual Studio debugger will attach to the process and enable debugging.
Next step: Download the demo app and try it your self.