Board Thread:General Discussion/@comment-33125777-20171120162229/@comment-24253265-20171120234014

Typically you'd put new categories like the not yet existing (=not yet created) Category:Type 0 in a parent category, e.g., Category:Types, and so on until you reach the existing hidden Category:Browse as root of the category tree.

There are some special pages to manage this: Special:WantedCategories lists wanted not yet created categories, Special:UncategorizedCategories lists existing categories without parent category, Special:UnusedCategories does what the name says, but empty categories can be okay.