Code

<?php
// contao/dca/tl_news.php
use Contao\CoreBundle\DataContainer\PaletteManipulator;

$GLOBALS['TL_DCA']['tl_news']['fields']['location'] = [
    'label' => ['Location', 'Location of the news entry, if applicable.'],
    'inputType' => 'text',
    'eval' => ['tl_class' => 'w50', 'maxlength' => 255],
    'sql' => ['type' => 'string', 'length' => 255, 'default' => ''],
];

PaletteManipulator::create()
    ->addField('location', 'title_legend', PaletteManipulator::POSITION_APPEND)
    ->applyToPalette('default', 'tl_news');

<script>
  (function() {
    if (navigator.cookieEnabled) return;
    var e = document.querySelectorAll('input[name="REQUEST_TOKEN"]'), t, c, i;
    for (i=0; i<e.length; i++) {
      c = e[i].parentNode;
      if ('formbody' !== c.className) return;
      t = document.createElement('p');
      t.className = 'error nocookie';
      t.innerHTML = '<?= str_replace("'", "\\'", $GLOBALS['TL_LANG']['ERR']['formCookieWarning']) ?>';
      c.insertBefore(t, c.firstChild);
    }
  })();
</script>