Just create a class library with your AppHost and drop it in the /plugins folder. The docs provides a link to the /example-plugins/Chat project used to create Chat.dll.
It doesn’t provide an IDE integrated debugging experience since it’s not a regular compiled & built dotnet app, I’d recommend configuring logging and analyzing your App through its log output, e.g:
LogManager.LogFactory = new ConsoleLogFactory(debugEnabled:true);
If needed you can attach to the running Sharp App process (i.e. x.exe or app.exe) and debug it that way.
The only other thing you can try is NetCoreTemplates/parcel-webapp which has scripts for running the client bundling & compiling the server plugin. Otherwise Sharp Apps isn’t going to be a good fit.