After T187770, we've got translation drafts to open with the same version of the editor with which they were started. So, when users starts a new translation, default version kicks in (that is CX1 for every environment except cx2-testing) and user can change the version manually by adding &version=2 to the URL.
After that, if user opens unpublished translation again, same version of CX will be used.
If user types &version=2 on dashboard, starting a new translation will not respect that choice and the default version will be used instead.