Usage: WINDOW ADDGROUP <name>
  Sets the server group to <name> for the window.  ircII will
  attempt to always keep windows with the same server group
  name connected to the same server.  i.e.:  If you set up
  windows 3, 5 and 6 as being in server group `foo', (with the

  WINDOW ADDGROUP foo

  command) then, when one of these three windows are connected
  to a server, the other two are also connected to this server.

See also
  WINDOW DELGROUP