The created sample based on your scenario also exhibit the same issue as you described. A bug report has been submitted to the developer. We will inform you if there is any update or progress regarding this issue.

Invisible column will not be rendered, so it will not be accessible from client side function. However, we could use hidden data member property on a visble cell to hold the hidden column value. Here is a snippet to set the hidden column description value in the key column in the PrepareDateBindind server side event:

WebGrid1.RootTable.Columns.GetNamedItem("description").Visible = false;
WebGrid1.RootTable.Columns.GetNamedItem("key").HiddenDataMember = "description";

During onAcceptAllChanges client side function you will need to access the cell element and retirve the description attribute:

var parentMod = grd.Tables["parent"].GetChanges("Modified");
for (i = 0; i < parentMod.length; i++)
{   
    parentMod[i].Row.GetCell("key").CellElement.getAttribute("description");
}

Using the WebGrid sample ProgrammaticExportServerside.aspx, and modifying the export type to xml, there is no exporting issue. The sample is using AccessDataSource.

Which DataSource did you used to replicate the issue?  

We could not replicate the issue using all the latest release build. The WebDesigner for WebGrid is referencing ISNet.WebUI.WebGrid.Editor.dll and ISNet.WebUI.Editor.v4.dll in the GAC. Please make sure those fole in GAC already has the same version and build with the WebGrid and WebUIFramework dll from your project folder.

We also suggest you to clear your temporary ASP.NET folder, default location in C:\Windows\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files, to remove any cache to the previous dll version.

You use sort the item alphabethically on EditType dropdownlist column if you are using WebValueList, just set the property UseValueListForSorting to true to sort it by tthe text value.

AutoFilterSuggestion will work with any dateformat if the column datatype is DateTime and the formatting is done using DataFormatString property of the WebGridColumn. For example here is the snippet to format column RequiredDate to displayed as "dd.MM.yyyy hh:mm:ss":

<ISWebGrid:WebGridColumn Caption="RequiredDate" DataMember="RequiredDate" DataType="System.DateTime"
    EditType="CalendarCombo" Name="RequiredDate" Width="100px" DataFormatString="dd.MM.yyyy hh:mm:ss">
</ISWebGrid:WebGridColumn>

Please execute the columnset creation code once. In the sample you attached, the columnset will be created each time PrepareDataBinding is triggered, if you only execute the code once (while page is not PostBack) the page will display without any issue.

You could try using AdvancedFilterExpression by disabling AutomaticFilter in the RootTable and handling the WebGrid filtering yourself in order to achieve filtering more than one item. Attached is a similar sample of filtering more than one City or Country