That’s a good idea! Unfortunately I couldn’t quite get it to work. However, by changing the width upon hover, I got something that seems to work OK. Is that close to what you wanted?
a.tag{
visibility: hidden;
width: 10px;
white-space: nowrap;
}
a.tag::before {
visibility: visible;
content: "#";
}
a.tag:hover {
visibility: visible;
width: fit-content;
}
a.tag:hover::before {
content: "";
}