@chapoi thank you for your patience with my inability to read the documentation 
I’ve now added a Theme Creator preview link to the top post, as it should have been from the start.
@Don @Heliosurge thanks a lot for the category and tag suggestions — great ideas, and I’ve shipped both in the latest version.
You can now restrict the auto-fill to specific categories, specific tags, or a combination of the two (when both are set, a topic has to match a category and carry one of the tags). Empty settings keep the old “run everywhere” behaviour.