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One more time it is important to mention that the fields are changed when documents are indexed in the multilingual context. And if any of the fields, different from “content“ and “title“, are marked as queryable then after indexing, this fields are changed (suffix added). So these new fields (the one with suffixed) should also be marked in the Workbench as Queryable.
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Content and title (with or without suffix) are automatically marked as queryable. All other should be manually marked.