Leave the website editor with its "Save" or its "Discard" button and wait for the editor to close. Discarding changes asks for a confirmation, which the step gives.
Examples
When I save the website editor
When we discard the website editor
And save the website editor
When I discard the website editor
And discard the website editor
Pattern
When(/^(I |we )*(save|discard) the website editor$/, …)
Part of @webship-js/odoo-steps (github.com/webship/odoo-steps), a step pack for Webship-js 2.0.x.