This is the documentation for the GoodNews back-end - or in MODX terms - the Manager Interface.
Each GoodNews mailing document is basically a MODX Resource enhanced with the necessary fields to define an email document. All mailing resources are stored "inside" GoodNews containers - which are also special MODX Resource documents.
Mailing resources will not be listed in the MODX Tree. Only their corresponding containers are treated like normal MOD Resource documents which are visible and handled within the tree.