<p><b>Products</b></p>
<ul class="products">
  <li class="product">01 <span>+</span></li>
  <li class="product">02 <span>+</span></li>
  <li class="product">03 <span>+</span></li>
  <li class="product">04 <span>+</span></li>
  <li class="product">05 <span>+</span></li>
  <li class="product">06 <span>+</span></li>
</ul>

<p><b>Wishlist</b></p>
<div class="box"></div>

function wishlistNewSt() {
    let cardBtns = document.querySelectorAll('.product span');
    let cardBox = document.querySelector('.box');
  
    for (let cardBtn of cardBtns) {
        cardBtn.addEventListener('click', () => {
            let item = cardBtn.parentElement;
            let clone = item.cloneNode(true);
            cardBox.appendChild(clone);
        })
    }
    return;
}
wishlistNewSt();