Hello,
You need to use WordFragments (https://www.phpdocx.com/documentation/practical/wordfragments-and-wordml). For example:
$textContent = new WordFragment($docx);
$textContent->addText('Hello world', array('bold' => true));
$list = array(
$textContent,
'Other text',
);
$docx->addList($list);
You can find more samples using WordFragments in the examples folder included in the package.
Regards.