In my deployment a request that was made was to change the default language to Danish. I discovered that it's possible via config.js by setting globalInterfaceLanguage="da_DK". I achieved this by making the nginx forward proxy serve a different config.js.

I think we should not try to generate the whole config.js, but an easier way to achieve the same is to simply append globalInterfaceLanguage="da_DK"; at the end of the config.js from the KV store before serving it.