.gutenberg__editor .block-editor-writing-flow span {
  background-image: url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='100%' height='6'><line x1='0' y1='5' x2='100%' y2='5' stroke='black' stroke-width='1' stroke-dasharray='4,2' /></svg>");
  background-repeat: repeat-x;
  background-position: 0 100%;
  background-size: 100% 6px;
  padding-bottom: 2px; /* pour laisser de l'espace au SVG */
}