After Grouping, when any change is made in the columns, that is, when expressions are added or columns are removed, then the modifications are not reflected in the GroupDropArea. You need to reset the Grouped Header collection so that the modification done in the columns can also be reflected in the GroupDropArea
You can use the GroupedColumns.Reset() method when the changes are done in the columns, to repopulated the Grouped Columns. In the following example, a column Id is grouped and then it is removed from the grid.
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