XMLRPC add shared roster group to the "displayed groups" of another group

I'm using the xmlrpc library to manage users on a server remotely.
I need to create shared roster groups and then add it to the "displayed groups" of another existing shared roster groups
The functions available for shared roster groups on this library are:

srg_create
srg_delete
srg_get_info
srg_get_members
srg_list
srg_user_add
srg_user_del

But none of them allow me to do what I need.

Please note, I'm not an Ejabberd expert and I call this functions from a .NET/C# application.

Seb.