You don't have to translate the data going to the server. Just translate the text of the button, and have it send a static string to the backend. In fact, looking at this line: https://github.com/edx/edx-platform/pull/654/files#diff-31e1e72e1a8b7aea06e0c665a351b511R46, the `dash_mode` isn't translated, it's just sent as the raw string, so it shouldn't be translated on the backend.