With R2 2016 GridViewComboBoxColumn will expose a property IsLightweightModeEnabled. Setting the property to True should resolve the problem.

The problem should be resolved with lib version 2015.3.1130.

GridViewDataColumn doesn't respect FallbackValue when the source property returns DependencyProperty.UnsetValue

The new properties will be available with Q2 2016. 

The issue is reproduced only with GroupRenderMode="Flat".

ClipboardCopyMode enumeration will expose a new property - SkipNullOrEmptyValue - setting whether null/empty value will be copied or not. Thus if copying cells from a column with multiple empty values, will not have a result in the pasted text, but rather be skipped.

The functionality is documented at http://docs.telerik.com/devtools/wpf/controls/radgridview/filtering/icolumn-filter-descriptors and for the time being the functionality can be achieved by implementing an attached behavior. 

I would like to be bale to modify at once several cells of a GridViewComboBoxColumn, when using the common ItemsSourceBinding for all rows (in my GridView, the selection ​is: SelectionMode="Multiple" SelectionUnit="FullRow").
So I would like for the selected rows to apply the same value as the edited cell.