While importing the arguments of the data validation rule, the formula is treated as text and its separators are replaced with the list separator defined in the current culture. This leads to an invalid formula treated as a list of strings.
RadSpreadsheetProcessing does not support chart color customization apart from selecting the color of the outline (set by Series.Outline.Fill). You cannot set the color of the fill of column charts etc.
Currently, row/column groups cannot be collapsed/expanded through the public API. User should be able to specify row's/column's "collapsed" attribute indicating whether the outlining is in a collapsed state.
Exporting empty workbook without any worksheet is not allowed according to the specification and such documents cannot be opened in Excel. Ensure the customers cannot create such documents using the API of SpreadProcessing.