You would need to get in touch with the developers, because this would require quite some coding, I guess. Write an email to the developer list or get in touch on the IRC channel.
1st question : what is a sub group ?
What reason to use "sub group"
Assistance on LimeSurvey forum and LimeSurvey core development are on my free time.
I'm not a LimeSurvey GmbH member. -
Professional support
-
Plugins, theme and development
. I don't answer to private message.