Deleting a post from the editorial calendar is very easy. Just drag and drop it into the area marked as trash at the top right of the calendar. To do that, just click on the post and drag the post around. Once the dragging begins, you’ll realize that there are new actions available next to the calendar, including the Trash area:
Just hover over that area whilst dragging the post and drop it on it (as depicted in the screenshot above). This will trash the post, so, as before, the action can be undone.
Unlike what happens with social messages, you can undo this operation. That is, if you trash a post, you can easily go to the trash (WordPress Dashboard » Posts » Trash) and Restore it.