See document (2.1) attached in EZP-25684
Copy pasting here to make it usable:

As an Editor
I want to create a new draft in a specific language simply
so that I can publish content in several languages

Acceptance Scenario: Editing accordingly to the language switcher state in View mode

Given I navigate to a content item view that has multiple language versions
When I change the language in the language switcher on the top right of the content widget
And click Edit in the action bar
Then a new draft is created and open in edit mode in the language selected