General developer forum

Please disregard this post and my foolish question.  That is what I get for not sleeping. 

I remember now that to get a category to appear as a sibling of the 'Site administration' category, I must define it in the plugin's local_foo_extend_settings_navigation() function in lib.php. For example:

function local_foo_extend_settings_navigation( settings_navigation $nav, context $context )
{
  $cat = navigation_node::create( 'Foo administration' );
  $nav->add_node( $cat );
}