This ticket describes the behaviors when a user decides to switch languages in the 'From'/'To' dropdowns:
=== Switching the //From// language:
 The language labels in the //From// column should change without affecting the //To// column.
 The image labels change to be in the new //From// language - only the ones which are not translated yet.
 If the translations are missing for some labels, the //From// column label should show 'Not provided' in the user's chosen language.
=== Switching the //To// language:
 The language in the //To// column can freely change if there are no translations added by the user yet.
 If a user tries to switch the //To// column after adding any translations, the added translations get lost. The user gets a confirm box before the language switches: //You are trying to change the translation language but you have unsaved translations. Changing the language will result in loss of any added translations. Please upload the translations to Commons or download the translated file before proceeding. Do you wish to continue? a) Change language b) Cancel//
**  The popup does not appear in the user has uploaded the file to Commons before trying to switch languages. It only needs to know clean/dirty and not if the content is the same as before.
 If the selected //To// language already has translations in the SVG, the inputs get populated with those translations.