/* Hide the fallback two-letter circle ("No"). */
.toolbar-button--icon--block-toggle-notifications .toolbar-button__icon {
  display: none;
}

/* Inject your icon. Update the path to your SVG. */

.toolbar-button--icon--block-toggle-notifications {
  display: block !important;
}
.toolbar-button--icon--block-toggle-notifications::before {
  content: "";
  display: inline-block;
  inline-size: 20px;
  block-size: 20px;
  margin-inline-end: .5rem;
  background-color: currentColor;
  -webkit-mask: url("/core/modules/navigation/assets/icons/error.svg") no-repeat center / contain;
          mask: url("/core/modules/navigation/assets/icons/error.svg") no-repeat center / contain;
}