With Shopify's native translation feature, the theme's translation is linked to every particular version of theme. This means that if you publish a new theme, the theme translation will not be migrated to the new theme automatically. We have a theme migration issue to help you bring over the theme text translations from one theme to another. You can watch this video, or continue reading this guide to find out how to use this feature.
This is not necessary to do with Basic Translations enabled, they will automatically update to replace your old translations with new ones.
You can use this feature by navigating to "Theme Migration" page in the App, either from the button on the left side menu of the button on the dashboard, as shown in the screenshot below.
Then, you will need to select the theme version you are migrating the translations from, and the theme version you are bringing the translations to.
If one of the theme versions that you want to migrate is not on the list, you can hit the "sync themes" button shown below to update the list to add new themes to the list.
Once you have selected both theme versions, you can hit the "Start Translation Migration" and the translation text of all languages will be migrated over from one theme to another.
Please note that text that is not from your theme will not need to be migrated, and is not affected by this migration.
If you have any questions about this feature, please let us know at firstname.lastname@example.org