You can turn a topic into a subtopic by assigning it a parent.
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.
Topic display order
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:
Create multiple taxonomies
We can create multiple taxonomies by exploiting topic display order and the fact that we don't show topics that don't contain articles for a given product.
Important: The key to making this work is to ensure that a product's articles don't share topics that are used in another product. This includes articles that redirect to other articles.