Using the "Translate Transcript" feature
Agents can request a translation of the transcript with a click on the kebab menu at the top and selecting Translate entire transcript:
This can be useful for example when a ticket is transferred from one agent to another, who does not speak the same language.
Note: This option is not enabled by default. To enable it, check the corresponding setting in your Application in Apps and integrations > Zendesk Support apps.
The Language IO plugin processes the translation and delivers it as an internal note in the chat for reference: