Catalina,
Unless I am missing something, dlg_manage() does not allow you to avoid setting Record-Route; how else will the endpoints know to send sequential messages through the proxy once the dialog is established?
The purpose of dlg_manage() is to provide an alternative to setting a flag for the purpose of indicating to Kamailio that the dialog the current INVITE seeks to establish should be statefully tracked and exposed to additional user-defined dialog module functionality (profiles, statistics, etc.) and other module functionality relying on internal API callbacks from the dialog module.
modparam("dialog", "dlg_flag", 4)
route { ...
# Process initial INVITE.
if(is_method("INVITE")) { ...
setflag(4); # Track this dialog.
}
}