[Resolved] Keep default language slug with language as parameter

Problem:
The client wanted to maintain the default language page slug/permalink (e.g., mydomain.com/welcome) while setting the language via a URL parameter (e.g., mydomain.com/welcome?lang=de for the German version), instead of using the page ID (e.g., mydomain.com/?page_id=1&lang=de). They also wanted to avoid manually translating menu items that link to an anchor on a specific page.
Solution:
We advised the client to activate the "Translate" option in WPML → Settings → Translated documents options to include the slug in the translation and prevent it from being created automatically from the title. This allows the client to copy the slug from the original page. For translating custom links in the menu, we provided a documentation link:
https://wpml.org/documentation/getting-started-guide/translating-menus/#translating-custom-links-after-wp-menus-sync.

Please note that the solution provided might be outdated or not applicable to your case. If the issue persists, we recommend opening a new support ticket. We also highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If you need further assistance, please contact us in the WPML support forum.