ext_localconf.php

<?php

defined('TYPO3_MODE') || die('Access denied.');

function configureT3quotesPlugin()
{
    \TYPO3\CMS\Extbase\Utility\ExtensionUtility::configurePlugin(
        'WDB.T3quotes',
        'T3quotes',
        ['T3quotes' => 'list,show,new,create,edit,update,delete'],
        // non-cacheable actions
        ['T3quotes' => 'create,edit,update,delete']
    );
}

function configureT3quotesWizards($v='')
{
    if ($v === 'v7') {
        // # Breaking #80700 Deprecated functionality removed (9.0)
        // # Breaking Deprecation: #78193 - ExtensionManagementUtility::extRelPath() (8.4)
        $icon = 'icon = ' . \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::extRelPath('t3quotes') . 'Resources/Public/Icons/user_plugin_t3quotes.svg';
    } elseif ($v === 'v8+') {
        $icon = 'iconIdentifier = t3quotes-plugin-t3quotes';
    }

    // wizards
    \TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPageTSConfig(
    'mod {
        wizards.newContentElement.wizardItems.plugins {
            elements {
                t3quotes {
                    ' . $icon . '
                    title = LLL:EXT:t3quotes/Resources/Private/Language/locallang_db.xlf:tx_t3quotes_domain_model_t3quotes.ce-wizard.name
                    description = LLL:EXT:t3quotes/Resources/Private/Language/locallang_db.xlf:tx_t3quotes_domain_model_t3quotes.ce-wizard.description
                    tt_content_defValues {
                        CType = list
                        list_type = t3quotes_t3quotes
                    }
                }
            }
            show = *
        }
    }'
    );
}

function addT3quotesIconToRegistry()
{
    $iconRegistry = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance(\TYPO3\CMS\Core\Imaging\IconRegistry::class);
    $iconRegistry->registerIcon(
        't3quotes-plugin-t3quotes',
        \TYPO3\CMS\Core\Imaging\IconProvider\SvgIconProvider::class,
        ['source' => 'EXT:t3quotes/Resources/Public/Icons/user_plugin_t3quotes.svg']
    );
}

$t3Version = TYPO3\CMS\Core\Utility\VersionNumberUtility::getNumericTypo3Version(TYPO3_version);
if (version_compare($t3Version, '8.0.0', '<')) {
    call_user_func(function () {
        configureT3quotesPlugin();
        configureT3quotesWizards('v7');
    //  addT3quotesIconToRegistry();
    }, $_EXTKEY);
} else {
    call_user_func(function () {
        configureT3quotesPlugin();
        configureT3quotesWizards('v8+');
        addT3quotesIconToRegistry();
    });
}

// cache for storing typoscript-constants
if (!is_array($GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['t3quotes_t3quotes'])) {
    $GLOBALS['TYPO3_CONF_VARS']['SYS']['caching']['cacheConfigurations']['t3quotes_t3quotes'] = [];
}

// Deutsche Übersetzungen
// $GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride']['de']['EXT:t3quotes/Resources/Private/Language/locallang.xlf'][] = 'EXT:t3quotes/Resources/Private/Language/de.locallang.xlf';
// $GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride']['de']['EXT:t3quotes/Resources/Private/Language/locallang_csh_tx_t3quotes_domain_model_t3quotes.xlf'][] = 'EXT:t3quotes/Resources/Private/Language/de.locallang_csh_tx_t3quotes_domain_model_t3quotes.xlf';
// $GLOBALS['TYPO3_CONF_VARS']['SYS']['locallangXMLOverride']['de']['EXT:t3quotes/Resources/Private/Language/locallang_db.xlf'][] = 'EXT:t3quotes/Resources/Private/Language/de.locallang_db.xlf';