This feature was available in StarOffice 5.2, but isn't available as an automatic feature any more. However, it's possible to simply size the spreadsheets appropriately and view them side-by-side.
Use Window > Split or Window > Freeze to help scroll more effectively through each.
You can also reduce the zoom by finding the zoom field at the bottom of the work area. Double-click it to bring up a window where you can specify any zoom, or right-click to get a list of commonly used zoom percentages like 75% and 150%.
This was first published in July 2006