Hide subcategories in Special:Category main menu
From semantic-mediawiki.org
Fragment of a discussion from Semantic MediaWiki Community Portal
> How could i maintain a tree view, making only (at this point) Category1 the only visible from the Special:category menu?
Generally, SMW (core) does not alter (or interferes with) the display of standard MediaWiki objects (such as categories). I'm not aware of any extension that would fit your requirement but maybe [0] can give you a starting point.
[0] https://www.mediawiki.org/w/index.php?search=category+tree&title=Special%3ASearch&go=Go