Make names of the Source Groups larger and bold (for screens wider than 480px)

Add this code to the Custom CSS field on the Appearance tab of your widget’s settings:

@media screen and (min-width: 480px) {
    li.yottie-widget-nav-list-item a {
      padding: 18px 16px 22px;
      font-size: 18px;
    }
}

If you want to apply changes for all screen sizes, use this code:

  li.yottie-widget-nav-list-item a {
      padding: 18px 16px 22px;
      font-size: 18px;
    }