See https://compo.sr/forum/topicview/browse/deploying/enable-forum-topic.htm?post_id=5330&topic_id=1214&timestamp=1543939416&redirected=1#post_5330

I've implemented support for setting defaults for new members (https://gitlab.com/composr-foundation/composr/commit/3f7d7cb57208165c8c18567bd6b7f23226d39010).

I haven't implemented support for mass-resetting for existing users, because I think that's questionable, and definitely less important. For example, what if a user has a more sophisticated setting already? What if there's a GDPR concern about opting people into things? What if you want to do it for only certain usergroups? I think this is something left out of the core product, people can do what they need with custom scripts in the rare case they need it.

I also haven't implemented support for setting defaults for individual categories (e.g. a particular news category), just the main notification types.