This was in the spec in T206712: Create the Translate view but got overlooked.
Current behavior
The To language dropdown defaults to user's chosen language for UI.
Desired behavior
- The To language dropdown by default always shows Select a language string. It does not matter what language(s) the user has added to their settings. They need to pick the language they want to translate to always. This string itself is localized into the language chosen by the user as the tool language. Opening this dropdown shows the ULS, as expected.
- Users should not be able to add translation labels unless they pick a language. The inputs are disabled until a To language has been selected.