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For a few back-end modules scripts are available to upload translated reference data.
The WolfCon 2023 lightning talk explains the details: Inventory reference data: Considerations for customizations, translations, system upgrades
mod-inventory-storage
https://github.com/zbw/folio-inventory-translations
https://github.com/gbv/folio-referencedata
mod-licenses
https://github.com/folio-org/mod-licenses/blob/master/scripts/upsert-licenses-refdata
Example file: mod-licenses-refdata-de.json
See also
DR-000012 - Localization parameter for back-end requires support for the HTTP Accept-Language header.