To include "/en/" in the URL for English content, it needs to be set up as the secondary language. The primary language won't display the language name in the URL slug, which is the expected behavior.
If you wish to change the default language to Chinese, please follow these steps:
2. Next, reconnect the Chinese language page to your English language page and designate your Chinese page as the primary language. You can find guidance on how to do this here: https://wpml.org/faq/how-to-link-already-translated-pages/
"To include "/en/" in the URL for English content, it needs to be set up as the secondary language. The primary language won't display the language name in the URL slug, which is the expected behavior."
We already have "/en/" in the URL for English content: hidden link
This is working.
The root URL is assigned to Chinese: hidden link
All we have done is change the default language to Chinese and translate the pages.