sass-site/source/assets/css/components/_navigation.scss

.sl-l-medium-holy-grail__body.sl-js-nav--is-sticky .sl-c-list-navigation-wrapper{
  position: sticky;
  top: 0;
  bottom: 0;
  overflow-y: scroll;

  @include sl-breakpoint--large { 
    height: 100vh;
  }
}

.skip-link {
  display: block;
  padding: 0.25em 1em;
  transform: translateY(calc(-100% - 1em));
  position: absolute;
  left: 1em;
  top: 1em;
  z-index: 9999;

  &:focus {
    transform: translateY(0);
    transition: all .1s ease-in-out;
    background: $sl-color--hopbush;
    color: $sl-color--white;
  }
}