If a column's TreeListOptionsColumn.AllowMove and TreeList's AllowColumnMoving properties are set to true, the column can be moved to a new position by dragging its header. By default, columns can only change their positions within their owning bands. To allow columns to change parent bands, enable the AllowChangeColumnParent option.
Note, that you can reorder columns in code without restrictions regardless of the AllowChangeColumnParent property's value.
The AllowChangeColumnParent property is not in effect when you customize bands using the Tree List Designer.