Groups in Guacamole

I try to set up some Guacamole connections with udm. First lesson learned: use append instead of set for ffurther parameters as shown here

univention-directory-manager guacamole/config create \
--position cn=guacamole,dc=domain,dc=com \
--set name=neu \
--set guacConfigProtocol="rdp" \
--append guacConfigParameter="" \
--append guacConfigParameter="enable-font-smooting=true" \
--append guacConfigParameter="" \
nestedGroup: 'Domain Admins,cn=groups,dc=domain,dc=com'

I’m not sure if quotes are needed. But the last line stopped me. I coudn’t figure out how to add a group. Always got an error

> nestedGroup: 'Domain Admins'
WARNING: the following arguments are ignored: "nestedGroup:" "Domain Admins"

Who knows the correct syntax to add a group here? I don’t want to add the permission group later in the gui.