#my-anchor-pseudo-element::before {
  content: '::before';
  margin-right: 1ch;
  background-color: var(--pseudo-element);
  anchor-name: --my-anchor-pseudo-element;
}

#my-target-pseudo-element {
  position: absolute;
  position-anchor: --my-anchor-pseudo-element;
  top: anchor(bottom);
  left: anchor(right);
}