The agent default language is the language Unbabel will assume the agent to understand and write in. It is used to establish the language pair for the translation requests in the ticket, along with the ticket (the customer's) language. Inbounds will have the agent's language as target text, while outbounds will use it for source.
The agent is the user able to change these definitions, by navigating the settings in the applet. Find the language definitions under Settings - Languages - By default you write in.
Changing the agent's language will trigger new translations if the resulting language pair is valid and if no translation in that LP exists prior to the change.
It is very important that this language is correctly set up, as it will determine the flow of all translation requests into our editor community. Any misconfiguration may result in wrong language pairs and compromise the quality and speed of delivery. For the normal use case, the agent language should remain English.