How do I delete an editorial task?

To delete a task within the edit post page, just hover the task you want to delete with your mouse (for instance, «Translate post»):

Editorial Task List
Screenshot of the editorial task box. It contains a list with all the tasks (completed, pending, and overdue) that are related to the current post.

so that available actions become visible:

Editorial Task Actions
While editing a post, hover over an editorial task with your mouse to reveal which actions are available.

The only possible action for a task—besides completing itis removing the task. Click on the Trash icon to delete the task.