.block-accordion .wp-block-details summary::after {
    content: '';
    border-bottom: 2px solid;
    border-right: 2px solid;
    content: '';
    display: block;
    height: 0.5em;
    position: absolute;
    right: 0;
    top: 45%;
    transform: translateY(-50%) rotate(45deg);
    width: 0.5em;
}

.block-accordion .wp-block-details[open] summary::after {
    top: 50%;
    transform: translateY(-50%) rotate(-135deg);
}

/**/