When using the NationBuilder Dropbox integration, there is no way to edit the template of an email notification or autoresponse. Without the dropbox integration, these HTML files are accessible via the "Theme" tab. With dropbox connected, a user is able to see but not edit them. Because they do not download to dropbox, there is no way to edit them with a dropbox account connected.
Thanks Brian - this is something that we will consider but does not have a timeline at the moment.