How to export CellCommentTips to Excel using GridExcelConverterControl

You can achieve this by handling QueryImportExportCellInfo event handler. In the event, check GridExcelTipStyleProperties for ExcelTip properties and accordingly add the comment to the IRange.

Syncfusion.GridExcelConverter.GridExcelConverterControl excelConverter = new Syncfusion.GridExcelConverter.GridExcelConverterControl();
excelConverter.QueryImportExportCellInfo += new Syncfusion.GridExcelConverter.GridImportExportCellInfoEventHandler(excelConverter_QueryImportExportCellInfo);

void excelConverter_QueryImportExportCellInfo(object sender, Syncfusion.GridExcelConverter.GridImportExportCellInfoEventArgs e)
{
    ExcelTip.GridExcelTipStyleProperties style = new ExcelTip.GridExcelTipStyleProperties(e.GridCell);
    
    if (style.HasExcelTipText)
    e.ExcelCell.AddComment().Text = style.ExcelTipText;
}
Dim excelConverter As New Syncfusion.GridExcelConverter.GridExcelConverterControl()
AddHandler excelConverter.QueryImportExportCellInfo, AddressOf excelConverter_QueryImportExportCellInfo

Private Sub excelConverter_QueryImportExportCellInfo(ByVal sender As Object, ByVal e As Syncfusion.GridExcelConverter.GridImportExportCellInfoEventArgs)
Dim style As New ExcelTipDLL.GridExcelTipStyleProperties(e.GridCell)
If style.HasExcelTipText Then
e.ExcelCell.AddComment().Text = style.ExcelTipText
End If
End Sub 'excelConverter_QueryImportExportCellInfo