See STORY 4 in the linked spec

BDD:

Given that I am viewing a Landing Page (which has no open drafts) in view mode,
When I click on the EDIT MODE Button,
Then, I enter the EDIT MODE of a new draft which was created from the Published version of the landing page I was previously viewing.
When I click on the PUBLISH BUTTON DROPDOWN,
Then, I see the list of available options.
When I click on SAVE DRAFT,
Then, my draft is saved and a confirmation notification appears.