I can't configure subcategories. They simply do not appear under the main category (for example, any%), but inside the leaderboard like a "bonus" variable. According to the solutions that I found, I configured them inside "Variables": name - Difficulty, Level - Full-game, Category - any%; and 2 variables - Easy and Hard. I was looking for a way to solve the problem under other similar topics on the forum, but maybe I misunderstand them and therefore I can’t create them. If it’s not difficult for anyone, discard the topic where they explained in detail (for stupid ones like me) how to do this in 2019 (maybe the changes have occurred and the topics that I looked at are already outdated).

Link to the game for clarity - https://www.speedrun.com/vapor_trail