Translations are managed under 'company data'. For translations to work, a spreadsheet with a list of translations plus a sheet with a list of languages needs to exist.
Translations data source
Term: Reference to the placeholder in the template that needs to be translated
IANA: en-GB, de-DE, etc. refers to the language choice made in a User Profile.
Language: List of languages the user can choose from
IANA: en-GB, de-DE, etc. refers to the column in the translations data source