Print taxonomy terms starting from specific slug in WordPress

print-tax.php

<?php
/*
 * Plugin Name: Print taxonomy terms starting from specific slug
 * Description: Usage: [print_taxonomy slug="product-category"] or <?php echo do_shortcode('[print_taxonomy slug="product-category"]'); ?>
*/

add_shortcode('print_taxonomy', function($atts, $content) {
	$atts = shortcode_atts( array(
		'slug' => '',
	), $atts, 'print_taxonomy' );
	$taxName = 'category';
	$terms = [];
	$terms[] = get_term_by('slug', $atts['slug'], $taxName);

	foreach($terms as $term) {
		echo '<a href="' . get_term_link( $term->slug, $taxName ) . '">' . $term->name . '</a>';
		$term_children = get_term_children( $term->term_id, $taxName );
		echo '<ul>';
		foreach ( $term_children as $term_child_id ) {
			$term_child = get_term_by( 'id', $term_child_id, $taxName );
			echo '<li><a href="' . get_term_link( $term_child->name, $taxName ) . '">' . $term_child->name . '</a></li>';
		}
		echo '</ul>';
	}
	return ob_get_clean();
});