This is a quick reference on how SUMO topics and subtopics work.
When you create a topic you must give it a name, a slug and a display order. The topic slug must be unique but the name and display order do not.
You can set whether a topic is visible or not. Topics that are not visible do not show up on product pages or in the sidebar. They are, however, accessible by their URL and they can be assigned to an article.
Visible topics and subtopics are displayed on product pages and the sidebar in numerical order (using their "display order").
If the current product doesn't have any articles in a particular topic or subtopic, that topic or subtopic will not be shown on the product page or in the sidebar. This is not the case for the "Related topics" section (see bug 877768).
The first 5 visible topics (that contain articles) are used as the main topics on the product landing page. A special topic, "Get Community Support" is always shown in the sixth (or last) position of this section.
The next 5 visible topics (that contain articles) are used as additional topics that are displayed, below the main topics, on the product landing page and in the sidebar.
SUMO Topic Admin:
Firefox Product Page:
For example, currently on stage (6/6/2013), we have a set of topics in use only by Firefox OS. These topics have unique slugs and, for the sake of organization, they have display numbers that are higher than the Desktop main and additional topics.