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The "All reviews" tab in Translate provides a great an overview of all recently published reviews including the most recent version number. It also indicates the version number most recently translated (if at all).
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The "Diff versions" button is available when a previous version has been translated. You can click the button to see which changes have been made in the English text to understand better how much work will be involved in updating the translation. See a step-by-step guide further details about that here.
If you would like to search for all out-of-date translations at once, you can do that by running a search in Archie. Please find step-by-step instructions here.
To update the previous translation, send the review to Phrase by clicking on the "Send to Phrase" button (if it hasn't been sent automatically already).
In Phrase, apply the Translation Memory to the translation file to utilise existing translations (if not done already). To do so, select the translation file and click on "Pre-translate", then "Pre-translate where empty...".
Next, select "Pre-translate from translation memory" (set to 100%), "Pre-translate non-translatables", and "Set segment status to confirmed for" "101% translation memory matches" and click "Pre-translate".
Then proceed with the regular translation process in Phrase.