Is there a way to create nested subcategories?

I’m trying to create subcategories in my knowledgebase, and can’t get them to display in an easy-to-find manner.

If you visit the link I submitted, the Visitor Management section at the bottom is what I’m referring to.

That category has a child category, “Other Label Printers.” However, it’s hard to see that plus sign that needs to be clicked on.

What I was hoping to have is the category display like it normally does, but instead of showing posts, it would show subcategories, which could then be clicked on to show posts.

Here is an image in Google Drive that shows what I’m dealing with now.

I’m guessing this is possible with CSS edits, but didn’t know if there was an easier way.

The page I need help with: [log in to see the link]