BuddyPress.org

@DJPaul Thanks for your response. I am not a programmer so

Folks at WPMU Dev suggested trying this pluggin by JohnJamesJacoby to see if it works:

WP Multi Network

https://wordpress.org/extend/plugins/wp-multi-network/

Adds a Network Management UI for super admins in a WordPress Multisite environment.
Turn your multi-site installation of WordPress into many multi-site networks, all surrounding one central user base.

WP Multi Network allows cape wearing super admins to create new network collections of sites, allowing for infinitely extensible site, network, and domain arrangements.

@johnjamesjacoby Please advise if I can use this pluggin for my purpose as I explained in the original post above.

Thanks you very much.