Open the layout editor ("Manage blocks") of a layout, by the name the list of layouts shows.
Examples
Given I am editing the "Default Layout" layout
Given I am editing the "Home page" layout
Given we are editing the "Dashboard" layout
And I am editing the "Default Administrative Layout" layout
Given editing the "Home page" layout
Pattern
Given(/^(I am |we are )*editing the "([^"]*)" layout$/, …)
Part of @webship-js/backdrop-cms-steps (github.com/webship/backdrop-cms-steps), a step pack for Webship-js 2.0.x.