Indicates the group action
If it is set to true, the action is canceled
The new IGroupDescriptor to be inserted
If the action is 'insert', the index of the new group descriptor is inserted before. If the action is 'reorder', the new index of the reordered groupDescriptor in the old collection is inserted before
If the action is 'remove', the groupDescriptor index is removed. If the action is 'reorder', the old index of the reorder groupDescriptor is used
Defines arguments of the event that occurs when the user updates groups with UI actions