I hope I’m understanding you correctly but what you would do is:
- Create your main surround output bus under VST connections
- Create various stereo child busses underneath the main surround output bus
- Add your various stereo group/FX channels and set their outputs to the required child bus
From your channels you can now send (or route/direct route) to your group/FX busses which then get passed to the appropriate channels on your main surround bus.