code: public function getExcludedFields()
  	{
  		$processed = array();
  
  		/** @var SplFileInfo[] $files */
  		$files = Contao\System::getContainer()->get('contao.resource_finder')->findIn('dca')->depth(0)->files()->name('*.php');
  
  		foreach ($files as $file)
  		{
  			if (\in_array($file->getBasename(), $processed))
  			{
  				continue;
  			}
  
  			$processed[] = $file->getBasename();
  
  			$strTable = $file->getBasename('.php');
  
  			Contao\System::loadLanguageFile($strTable);
  			$this->loadDataContainer($strTable);
  		}
  
  		$arrReturn = array();
  
  		// Get all excluded fields
  		foreach ($GLOBALS['TL_DCA'] as $k=>$v)
  		{
  			if (\is_array($v['fields']))
  			{
  				foreach ($v['fields'] as $kk=>$vv)
  				{
  					// Hide the "admin" field if the user is not an admin (see #184)
  					if ($k == 'tl_user' && $kk == 'admin' && !$this->User->isAdmin)
  					{
  						continue;
  					}
  
  					if ($vv['exclude'] || $vv['orig_exclude'])
  					{
  						$arrReturn[$k][Contao\StringUtil::specialchars($k.'::'.$kk)] = isset($vv['label'][0]) ? $vv['label'][0] . ' <span style="color:#999;padding-left:3px">[' . $kk . ']</span>' : $kk;
  					}
  				}
  			}
  		}
  
  		ksort($arrReturn);
  
  		return $arrReturn;
  	}
docs: Return all excluded fields as HTML drop down menu
  
  @return array