Plugin content element (list) and the plugin sub types field (list_type) have been marked as deprecated

[nebrot]

The plugin content element (list) and the plugin sub types field (list_type) have been marked as deprecated in TYPO3 v13.4 and will be removed in TYPO3 v14.0. These changes are at least needed. A upgrade wizard should also be added (don't have knowledge about this topic).

ext_localconf.php (PLUGIN_TYPE_CONTENT_ELEMENT as fifth parameter):

\TYPO3\CMS\Extbase\Utility\ExtensionUtility::configurePlugin(
    'typoscript2ce',
    'Pi1',
    [
        \In2code\Typoscript2ce\Controller\TypoScriptController::class => 'index'
    ],
    [
        \In2code\Typoscript2ce\Controller\TypoScriptController::class => $uncachedActions
    ],
    \TYPO3\CMS\Extbase\Utility\ExtensionUtility::PLUGIN_TYPE_CONTENT_ELEMENT,
);

tt_content.php (whole file):

<?php

$pluginSignature = TYPO3\CMS\Extbase\Utility\ExtensionUtility::registerPlugin('typoscript2ce', 'Pi1', 'Typoscript2ce');

TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addToAllTCAtypes(
    'tt_content',
    '--div--;Configuration,pi_flexform,',
    $pluginSignature,
    'after:subheader',
);

TYPO3\CMS\Core\Utility\ExtensionManagementUtility::addPiFlexFormValue(
    '*',
    'FILE:EXT:typoscript2ce/Configuration/FlexForms/FlexFormPi1.xml',
    $pluginSignature,
);

Also the compatibility have to be changed in ext_emconf.php + composer.json.

Sources:
https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/13.4/Deprecation-105076-PluginContentElementAndPluginSubTypes.html
https://docs.typo3.org/m/typo3/reference-coreapi/main/en-us/ApiOverview/ContentElements/MigrationListType.html