Spreadsheet Workbook Properties

How can I get/set the underlying XLSX workbook properties (POIXMLProperties - title, subject, keywords, description) from the Vaadin Spreadsheet API?

Unfortunately, you can’t. It was a conscious design decision not to duplicate POI API in Spreadsheet. So you need to get the workbook from the spreadsheet, use whatever POI APIs you need to , and then tell spreadsheet to reload the file.