How does "sorting=user defined" within a plan view work?

Thanks Aradhya, you write "This order is persistent". I have now set "sorting=user defined". This works. But how do I now define on which column it should persistent sort? I can click on column headers and the plan or the group will be sorted by this column. But on refresh the sort is changed to an unknown default (I think Id).

Hi Guido When sorting is "User Defined" its not based on any of the work item attributes. User will define the order by rearranging the work items in the list and the same order will be retained. For Example if below is the default order and user wants Task 3 to appear before Task 1 then he can just drag task 3 above task 1 and this order will be retained. Parent Story Task 1 Task 2 Task 3

The only difference between this and Ranking is that when user rearranges the work items then the ranking of the work item is changed. But in User Defined the ranking does not change.