Follow these steps to mark changed translations in the Default Reference Language, to have contributors easily review the corresponding translations in the other languages.
1. Update translations in Default Reference Language
If you use the import in the Project page, choose to Also import translations in…, select the Default Reference Language (English in the screenshot), check the box to overwrite old translations, and then select the option to mark corresponding translations from the other languages as fuzzy for the updated values.
After hitting Import File, you'll be able to delete obsolete terms (terms which are no longer in the file, but are still in the project).
If you use the import in the Language page, choose that you want to overwrite old translations and to mark corresponding translations from the other languages as fuzzy for the updated values.
2. Notify contributors
In the Project page, there is a Notify Contributors button in the side menu. Use it to let contributors know about the changes, and tell them to review the fuzzy translations in the languages they are assigned to. They can easily order the translations by fuzzy first or choose to see only these translations using the filters at the top of the language page.
After review, they can use the Toggl Fuzzy Translation button (F button next to the translation) in the Language Page to remove the fuzzy flag.