.wp-block-rank-math-toc-block
{
    position: relative;
}
.wp-block-rank-math-toc-block h2
{
    background: #f1f2f6;
    padding: 10px 12px 10px 18px;
    cursor: pointer;
    font-size: 18px!important;
    font-weight: normal!important;
    position: relative;
    margin-bottom: 0;
}
.wp-block-rank-math-toc-block h2:before
{
    display: inline-block;
    content: "";
    width: 0;
    height: 0;
    border-style: solid;
    border-width: 6px 0 6px 12px;
    border-color: transparent transparent transparent #000;
    margin-right: 8px;
}
.wp-block-rank-math-toc-block nav
{
    padding: 10px 10px 0 10px;
    max-height: 0;
    overflow: hidden;
}
.wp-block-rank-math-toc-block input:checked+h2~nav
{
    max-height: 100vh;
    overflow: visible;
}