As I was figuring out how to show filtered lists of blog posts, I came across the HTML summary and details tags. I put the title of the list in the <summary> tag, and the list itself in <details>. When you click the <summary> tag, it will toggle display of whatever is in <details>. Handy for simple dropdown lists without javascript. Check it out - I hope it helps you!

There are a bunch of html tags that are not often used but that can be really helpful.