Although the theme has drop-down nested menus for languages and versions, there seems no way to create custom drop-down menus. Which is an issue if your documentation site is very large.

I have managed to create them by modifying navbar.html and adding the menu entries to config.toml (using the parent field), but shouldn't this be built into the theme? It would be great if you could just define a sub-category in the frontmatter and it appears in the horizontal menu as a nested menu item.