How do I center a line, a verse or a dedication? Can I justify or left-align a paragraph?

From version 1.9.15: click in the paragraph and click Center or Align right in the toolbar above the editor. The whole paragraph is aligned; for a verse, keep its lines together (press Enter once between lines, not twice) and they are centred as one block. Click the same icon again to go back. There are no Justify or Align left buttons on purpose: the alignment of ordinary paragraphs comes from your book's design, so that every page of the book looks the same. Center and Align right are for the places that need them: a verse, a dedication line, a signature, a date.