Hierarchy facet – only show innermost depth items

<?php

// Add to your (child) theme's functions.php

add_action( 'wp_head', function() {
?>
<script>
document.addEventListener('facetwp-loaded', function() {
    let $facet = fUtil('.facetwp-type-hierarchy');

    if ($facet.len()) {
        let depthNodes = $facet.find('.facetwp-depth').nodes;
        let lastDepthNode = depthNodes[depthNodes.length - 1];
        $facet.find('.facetwp-link').addClass('facetwp-hidden');
        fUtil(lastDepthNode).find('.facetwp-link').removeClass('facetwp-hidden');
    }
});
</script>
<?php
}, 100 );