For any serious game development with advanced techniques like Source Generators, you’ll need a full blown IDE. VS Code is not an IDE, it’s just a code editor (i.e. a fancy Notepad). There could be ways to make it behave like an IDE via plugins, but it’s fragile and can never reach the potential of a full blown IDE that has those features already baked in from the get go.
So I highly advice you to switch to Visual Studio or Rider, so you can struggle with your game code instead of fighting against the tools.