Hi Deborah

The tool that is used to navigate through learning resources is the courses catallogue. The course catalogue in Totara 12 can be configured to display content in a variety of ways including block formats, images and selected content.

If you add a Filter for Course category - this will allow the user to select the categories they are interested in.

It is also possible to use audience based visibility so learning resources are only visible to selected users.

It is more about configuring the catalogue and visibility settings rather than a specific number of categories required.

Regards