Center links and remove padding from folders

Here's an option that worked okay for me within the CSS Editor:

.header-nav-folder-content {
  text-align: center !important;
  padding:2px !important;
  max-width: 100% !important;
  margin-right: 15px !important;
}

Important Note: this works well if you have a folder title that's a bit longer and the pages within the folder don't have exceptionally long titles. If you have a folder with a really short title, the code above is going to make each navigation link within the folder wrap to multiple lines which may not be ideal.

If you're planning to use shorter folder titles and longer links within that folder, try this instead so there's more room for your navigation link text:

.header-nav-folder-content {
  text-align: center !important;
  padding:2px !important;
}

Hope this helps someone else!