Attempt for duplication feature

When scanning trough the code I acutally saw, that there is already method duplicateChild in collections.grid.resources.js in the mgr assets, so I then managed to let a "duplicate" button show up in the collections grid by adding it to the getlist.php processor. After that I tried to attach the duplicateChild() method to this button by editing the method in collections.grid.resources.js...

but unfortunately this doesn't seem to be enough as the button doesn't work as desired, instead I'm redirected to a 404 page /manger/undefined...tried to follow the request in the inspector, but the request to the resource processor is canceled, so nothing to see...any ideas where this could be stuck? I really suck in extjs, but was worth a try =)...hop to see this soon!