OBSOLETE: How to change the field grouping and sort order in the Field List

Update: starting with version 16.1 it is possible to sort fields and folders using the CustomCustomizationFormSort event. 

To accomplish this task, it is necessary to create a custom Customization Form descendant, and override the PivotCustomizationFieldsTree.AddNode method. To control node sort order, use the PivotCustomizationTreeNode.GroupPosition property. Automatic nodes return GroupPostion in interval [0..5]. It is necessary to return smaller or greater numbers to place nodes before or after default nodes.