[Nexus]

var spoilers = [].slice.call(document.querySelectorAll('SPOILERS-SELECTOR'));
if (!spoilers.length)
    return;

var btn = document.createElement('button');
btn.type = 'button';
btn.innerHTML = 'Button';
btn.addEventListener('click', function() {
  spoilers.forEach(function(node) {
      node.dispatchEvent(new Event('click'));
  });
});
              
spoilers[0].parentNode.inserBefore(btn, spoilers[0]);