Long description

add_action('rank_math/vars/register_extra_replacements', function () {
    rank_math_register_var_replacement(
        'long_desc',
        [
            'name'        => esc_html__('Long description', 'rank-math'),
            'description' => esc_html__('Product long description', 'rank-math'),
            'variable'    => 'long_desc',
            'example'     => long_desc_callback(),
        ],
        'long_desc_callback'
    );
});
function long_desc_callback()
{
    return wp_strip_all_tags(get_the_content());
}