in the EditorOverlay and CollectionEditorOverlay in Gather we have logic for various screens e.g. edit, preview, save
Despite this there is no easy way to do this without editing the entire template or hacking the partial by using overlay-sub-header elements
Let's talk about how we could do this better and find a better approach
e.g. Overlay.prototype.screens = { header: headerOptions, content: contentOptions, template: template }
(see https://gerrit.wikimedia.org/r/#/c/215368/1)