If you're talking about the Tutorials forum then the forum structure has been kept as simple as possible and I really doubt that any sub-forum would be added; because they cause confusion. You can use topic tags and prefixes, so that those topics get displayed when a certain genre is searched for.
If you're talking about the built-in tutorials, that was suggested once on the legacy GMC but the suggestion was denied because classifying tutorials on the basis of genre is a bad idea. Those tutorials are mere demonstrations of how certains functions can be used and not really engines of various genre mechanics. So I highly doubt the effectiveness of such a system.