ext_localconf.php

<?php
// declare(strict_types = 1); // only possible for TYPO3 >= v12

use TYPO3\CMS\Backend\Form\Container\FilesControlContainer;

defined('TYPO3') or die();

if(!defined('TYPO3_PIXXIO_EXT_NUM')) {
    define('TYPO3_PIXXIO_EXT_NUM', 1554937800);
}

$GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride']['de']['EXT:pixxio_extension/Resources/Private/Language/locallang_be.xlf'][] = 'EXT:pixxio_extension/Resources/Private/Language/Overrides/de.locallang_be.xlf';

if (\TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Information\Typo3Version::class)->getMajorVersion() < 12) {
    // adds pixx.io button by overwriting TYPO3 InlineController
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['nodeRegistry'][1554937800] = [
        'nodeName' => 'inline',
        'priority' => 55,
        'class' => \Pixxio\PixxioExtension\Backend\InlineControlContainer::class,
    ];

} else {
    // adds pixx.io button by overwriting TYPO3 FilesControlContainer
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['nodeRegistry'][1554937800] = [
        'nodeName' => FilesControlContainer::NODE_TYPE_IDENTIFIER,
        'priority' => 55,
        'class' => \Pixxio\PixxioExtension\Controller\FilesControlContainer::class,
    ];
}

/**
 * Add Icon for BE Module
 */

$iconRegistry = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Imaging\IconRegistry::class);
$iconRegistry->registerIcon(
    'actions-pixxio-extension-modal-view',
    \TYPO3\CMS\Core\Imaging\IconProvider\SvgIconProvider::class,
    ['source' => 'EXT:pixxio_extension/Resources/Public/Icons/Extension.svg']
);
unset($iconRegistry);