Is there a way to make a clickable dropdown menu in a .yml file?

Question

I have a YAML file used to create a navigation bar for my website. The navigation bar works properly, but I'd like to add more functionality to it. Specifically, I want to be able to click on certain pages in the navigation bar and either access dropdown menus or navigate to specific pages.

Here is a simplified version of my current YAML file:

navbar:
  title: "Alex Pettis"
  left:
    - text: "Home"
      href: index.html
    - text: "Courses"
      href: "javascript:void(0);"
      menu:
        - text: Undergraduate
          ...
        - text: Graduate
          ...
    - text: "Resume"
      href: Resume.html
    - text: "Software"
      href: Software.html
output:
  html_document:
    theme: yeti

I've tried modifying the href attribute for the "Courses" dropdown menu to javascript:void(0);, but it didn't work as expected. Also, I tried adding the submenu: below the href: "courses.html" but it doesn't make the menu drop down. Is there a way to make the "Courses" dropdown menu expand when clicked and also be able to navigate to the "Courses" page when the top-level "Courses" text is clicked?