var buttonChange = document.querySelector('#dns-content-nameservers button');

buttonChange.click();

setTimeout(function() {
  var radioCustom = document.querySelector('#nameserver-type-CUSTOM'),
      list = ['new nameserver #1', 'new nameserver #2', 'new nameserver #3', 'new nameserver #4'];
      
  radioCustom.click();
  
  setTimeout(function() {
    var buttonAdd = document.querySelector('#addCustomNameserver');
    buttonAdd.click();
    buttonAdd.click();
  }, 550)
  
  list.forEach((l) => {console.log(l)})
}, 750);