Navigate to Notebook and open the entry you would like to modify.
Hover over the data block and click on the crossed arrow icon that appears at the top-right corner.
While keeping the button pressed, drag the data block around in the entry. The area initially colored in light blue will be highlighted in dark blue when you hover over it, indicating that you will place the block there.
Release the button to settle the block. Please keep in mind that you can have up to two columns in your entry per row.