Hi Kevin,
Sorry for the delay, I've been packing boxes all weekend for moving house next week(ish).
The 'parents' option is only supported in the REST api, see
http://nagrestconf.smorg.co.uk/documentation/restreference.php#_hosts - it has an X in the flags column.
I have not yet had to use this option but understand that it's very useful so I will add it to the Issue Tracker for inclusion in the next release. (Issue #17)
As a workaround you could use the REST api to add the option. If the REST commands are added to a script then the script would need to be run after a configuration is applied. Unfortunately this would need to be done after each 'Apply Configuration'.
Cheers!
Mark.