I have tried to create a table view which would include a column for the previous workflow task owner. It would be helpful for users to see who has completed the task before them. I tried a few things under the "customization" option of the table view, however, I can't find a list item that describes the previous task owner. Note: "Modified By" is not helpful as there are not always changes made to the object before it reaches the next task. It can be deceptive. I have also chosen "predecessor", however, this column is always blank so I'm not quite sure what this item is supposed to list. Anyone have any suggestions?
Predecessor is not for the tasks, but for the PBO. You might be able to get what you want by displaying the users for the various roles that the workflow uses. It wouldn't give you exactly the one user immediately previous to the current. That is probably only visible in the object history or through the workflow itself.
If you want to get exactly what you want, you would need to develop some java that finds all of the related tasks and then selects the owner of the most recently completed one. Wouldn't know where to direct you from there though.
This information is readily available on the OOTB Process Tab in the Process Status Table where Users can see the name of the assignment, the assignee, the role of the assignee, Vote, Comments, and completion (By, Due Date, Date Completed).
If at all possible I would recommend leveraging this OOTB capability as to have this information appear in the Users Tasks Table would require some non trivial work. What shows up in the Tasks Table is a Work Item and everything you see are attributes of the Work Item Object. The preceding assignment would be a different Work Item Object, linked to the same process object. You would have to add attributes to the Work Item and develop code in the workflow (process) to pass information from one to the other. Doable, but why when the information is already visible elsewhere?
I understand that we can get the above information in the "related" tab under the workflow. However, the users specifically require the ability to sort by previous owner in the My Task window. There are times when they need to blitz on a specific user. It would be helpful for them to sort by that user so that they only see those tasks. FYI, there can be hundreds of workflow tasks in the My Tasks window so this functionality would be very helpful.
Being inherently lazy, if I were faced with the same requirement I would look at developing a Report. I developed a report for users to "see" both their assignments and the "Need Date" of the PBO together. The approach here would be similar... SELECT on Work Items with CURRENT_USER as "Owner", join with Process, joined with Work Items with Completed Status AND [some_user as Parameter] as Owner. It would probably take a bit more to get only where the some_user was specifically the Owner of the last completed... but would get you a return of some_user as Owner has completed a Work Item on the same process.
I wrote out what I thought would need to happen and then cut it from my response as it was fairly convoluted when I read it. If the report does not work for you let me know and I'll share my convoluted concept.