Hi,
Please find attached "ObjectsToForest" script that'll automatize that process (add items & place them to source object's position). Use the Select Objects to pick all objects that should be inserted into the new "AutoForest" object. Than by clicking the AutoForest button, it'll create a new Forest object with all those objects with transformations corresponding to its "source objects".
Hope it'll be a good time saver for your task.
Best regards,