.wp-block-genesis-custom-blocks-sub-multi-content {

}
.wp-block-genesis-custom-blocks-sub-multi-content .genesis-custom-blocks-editor__ssr {
  border: 1px dotted #a4a4a4;
}
.wp-block-genesis-custom-blocks-sub-multi-content .genesis-custom-blocks-editor__ssr::before {
  content: "リスタ：サブコンテンツ";
  padding: 10px;
  display: block;
  color: var(--wp--preset--color--contrast);
}