I've never used ZK Spreadsheet but I think this could be the same behavior that in a classic listbox. In a listbox you have to use a listbox in mold 'select' instead a combobox, like this bellow. Bogliolo Patologia Geral Pdf here.
ZK Spreadsheet for XPages. ZK is a highly productive. Such as ZK Spreadsheet. Installation Steps Working with ZK Spreadsheet. ZK is the leading open source Ajax and mobile framework designed to maximize enterprises operation efficiency and minimize the development cost. ZK Spreadsheet for XPages. ZK is a highly productive. Such as ZK Spreadsheet. Installation Steps Working with ZK Spreadsheet.
limieagle – 2018