Great stuff!
I maked some customized changes to show the link at the bottom.
a.external-link {
position: relative;
}
a.external-link:before {
position: fixed;
left: 0;
bottom: 0;
padding: 0.2em 0.6em 0 0.6em;
color: var(--text-normal);
background-color: var(--background-primary-alt);
border-radius: 0 0.4em 0 0;
font-size: 80%;
display: none;
z-index: 1000;
content: attr(href)
}
a.external-link:hover:before {
display: inline;
}