Glad you like the plugin! :)
The Random tab does not allow selecting scene groups as I just could not think of a scenario where this would be useful.
Maybe this was just a bad judgement call on my side.
Could you describe your use case for the scene groups on the Random tab in a bit more detail?
But in general this is not a strict limitation - I could allow selecting scene groups there at any time.
You can find a build where this is enabled here in a couple of minutes:
	
	
		
			
				
			
			
				
				An automated scene switcher for OBS Studio. Contribute to WarmUpTill/SceneSwitcher development by creating an account on GitHub.
				
					
						
							
						
					
					github.com
				
 
			 
		 
	 
(You will have to be signed into GitHub to be able to download it - let me know if that is an issue for you)