TypoScript

TypoScript constants should be stored in a file called constants.typoscript and TypoScript setup in a file called setup.typoscript.

These two files are made available for inclusion in TypoScript records with ExtensionManagementUtility::addStaticFile in the file Configuration/TCA/Overrides/sys_template.php:

<?php

use TYPO3\CMS\Core\Utility\ExtensionManagementUtility;

defined('TYPO3') or die();

ExtensionManagementUtility::addStaticFile(
    'my_extension',
    'Configuration/TypoScript/',
    'Examples TypoScript',
);

It is also possible to use subfolders or a differently named folder. The file names have to stay exactly the same including case.