Add Btn

function.php

//Este es el javascript del boton
function addBtnDirector(){
<sccript>
  let btn = document.querySelector('a.btndirectors');
  btn.addEventListener('click',function(e){
    e.preventDefault();
    let nav = document.querySelector('ul.masonry-filter');
    nav.classList.toggle('mostrar');
});
  </script>
}

add_action('wp_footer','addBtnDirector',10);

style.css

//Aca el CSS para ocultar 
.mostrar{
  display:block;
}

work.html

<a href="#" class="btndirectors" style="
    color: #131313;
    font-weight: 700;
    border: 3px solid #111;
    padding: 10px 28px;
    margin: 10px 0;
    display: inline-block;
"> + Show Directors</a>