Hello,
Thanks for posting the license you are using.
Tabs are paragraph styles, and you can't mix text paragraph styles to list item styles, only run-of-text styles can be applied. The best solution is using a custom paragraph style with the tabs styles set, imported from an existing DOCX or created from scratch, and set it to the list using the pStyle option (https://www.phpdocx.com/api-documentation/word-content/insert-list-nested-Word-document-with-PHP); or using the useWordFragmentStyles option with custom paragraphs styles available in the addList method too.
The addList/sample_5.php sample included in all packages illustrates how to apply the useWordFragmentStyles option.
Regards.