ext_tables.php

<?php
if (!defined('TYPO3_MODE')) {
   die('Access denied.');
}

if (TYPO3_MODE === 'BE') {

   /**
	* Registers a Backend Module
	*/
   \TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerModule(
	   'MASK.' . $_EXTKEY, 'tools', // Make module a submodule of 'admin'
	   'mask', // Submodule key
	   'top', // Position
	   array(
	   'WizardContent' => 'list, new, create, edit, update, delete, purge, generate, showHtml, createMissingFolders, hide, activate',
	   'WizardPage' => 'list, new, create, edit, update, delete',
	   ), array(
	   'access' => 'admin',
	   'icon' => 'EXT:' . $_EXTKEY . '/Resources/Public/Icons/module-mask_wizard.svg',
	   'labels' => 'LLL:EXT:' . $_EXTKEY . '/Resources/Private/Language/locallang_mask.xlf',
	   )
   );

   \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::registerAjaxHandler(
	   'WizardController::checkFieldKey', 'MASK\Mask\Controller\WizardController->checkFieldKey'
   );

   \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::registerAjaxHandler(
	   'WizardController::checkElementKey', 'MASK\Mask\Controller\WizardController->checkElementKey'
   );
}
\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addStaticFile($_EXTKEY, 'Configuration/TypoScript', 'Mask');

// include css for styling of backend preview of mask content elements
$TBE_STYLES['skins']['mask']['name'] = 'mask';
$TBE_STYLES['skins']['mask']['stylesheetDirectories'][] = 'EXT:mask/Resources/Public/Styles/Backend/';
//$TBE_STYLES['skins']['mask']['stylesheetDirectories'][] = "/" . $settings["backend"];

$storageRepository = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('MASK\\Mask\\Domain\\Repository\\StorageRepository');
$configuration = $storageRepository->load();

if (!empty($configuration)) {
    $tcaCodeGenerator = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('MASK\\Mask\\CodeGenerator\\TcaCodeGenerator');

    // allow all inline tables on standard pages
    $tcaCodeGenerator->allowInlineTablesOnStandardPages($configuration);
}