Shorten's breadcrumb to only show current & parent page when on mobile & tablet.

detailed-breadcrumb-mod.css

/* Shorten Breadcrumbs on Tablet and Smartphones */
/* Coded by Dan Jones */

@media only screen and (max-width: 1024px) {
  ul.sm-breadcrumb > li.sm-breadcrumb-item {
    display:none;
  }

  ul.sm-breadcrumb li:nth-child(1), ul.sm-breadcrumb li:nth-child(2), ul.sm-breadcrumb li:nth-last-child(1), ul.sm-breadcrumb li:nth-last-child(2), ul.sm-breadcrumb li:nth-last-child(3), ul.sm-breadcrumb li:nth-last-child(4) {
    display:inline-block;
  }

  ul.sm-breadcrumb li:nth-child(2)::after {
    content:"...";
  }
  
  ul.sm-breadcrumb li:nth-child(2):nth-last-child(2)::after, ul.sm-breadcrumb li:nth-child(2):nth-last-child(4)::after {
    content:"";
  }
}

@media only screen and (max-width: 640px) {
  ul.sm-breadcrumb > li.sm-breadcrumb-item {
    display:none;
  }
  
  ul.sm-breadcrumb li:nth-child(1), ul.sm-breadcrumb li:nth-child(2), ul.sm-breadcrumb li:nth-last-child(1), ul.sm-breadcrumb li:nth-last-child(2) {
    display:inline-block;
  }
  
  ul.sm-breadcrumb li:nth-child(2):nth-last-child(2)::after {
    content:"";
  }
  ul.sm-breadcrumb li:nth-child(2):not(:nth-last-child(2))::after {
    content:"...";
  }
  ul.sm-breadcrumb li h1 {
    font-size:14px;
  }
}