On, we made a patch that included a stub Topic page for api.drupal.org (i.e., a @defgroup) titled:
Configuration and State Systems
This can be found in file core/modules/system/core.api.php where it says
The documentation to go on this page needs to be written. The idea is:
a) Write a few paragraphs about the topic.
b) Link to more detailed documentation on
c) If the more detailed documentation does not yet exist, create stub page(s), link to the stub pages, and add a note to this issue stating that the stub pages need to be filled out.
d) If the topic has related classes, interfaces, and functions, add
to their documentation headers. That will make these classes etc. show up on the Topic page on api.drupal.org.
For more info -- documentation standards for @defgroup/@ingroup: