title: Adding own CSS to TYPO3 backend [v9]
body: <p>I am trying to add some CSS styles to the TYPO3 backend (v9). I've added the stylesheet and the following line to the <code>ext_tables.php</code> of my own extension (as described in the file <code>typo3/sysext/backend/Classes/Template/DocumentTemplate.php</code>).</p>
  
  <pre><code>$GLOBALS['TBE_STYLES']['skins'][$_EXTKEY]['stylesheetDirectories'] = ['EXT:my_extension/styles.css'];
  </code></pre>
  
  <p>When I check the configuration, the new entry show up, so that looks fine. But I don't see any style changes to the backend.</p>
  
  <p>Any ideas anyone? Thanks!</p>