Thanks to #48 the user can now create new posts and pages. But what if they want to then discard a newly drafted post/page?

With the current implementation, in order to "undo" a newly created post/page the user must leave the Customizer and discard all other changes that they might have staged in the session.

Additionally, it seems reasonable that the user should be able to trash posts/pages that are pre-existing, just as they can inside post.php.