Hi Alex
The find learning catalogue shows results from courses , program, certification, playlists , resources.
Tags can be added to each of these by going to the area and going to Edit settings and typing in the tag required if it exists if will be in the list or if not it will be added as a standard tag.
Then the catalogue can be configured to include tags in the filter
An alternative that doesn't involve tags and displays less items in the filter and prevents mistyping of tags would be to add a course custom field - menu of choice for mandatory or optional values and include the custom field as a filter on the catalogue.
Regards