You can expand or collapse cells to get better sitemap preview and clear up space.
Each cell that has its child pages contains small + or - sign at the bottom cell border.
To expand the cell to see its child pages, click the small + sign at the bottom cell border.
To collapse the cell click the small - sign at the bottom cell border.
If you want to collapse/expand all pages on your sitemap at the same time, just open the File menu and click Collapse All or Expand All.