Wikidocumentaries offers links dynamically from its pages to Content Translation. However, CX has been made optional in many language Wikipedias, and the link does not always not work. Adding a campaign tag would allow it to bypass the default settings of the Wikipedia, if I understand correctly.
- Wikidocumentaries is at https://wikidocumentaries-demo.wmflabs.org/
- Navigate to a topic for which there is no article in the user's language
- Choose "Read the article in another language" below the header image
- While in the other language article, choose the "Read the article in another language" menu again
- Select "Translate this article to your language"
- Enter Content Translation