Draw the process diagram, to assign a task(which is already assigned) to another user

I have a process diagram as below.

Here Manager can view all the tasks which are unassigned and assigned to the particular developer.
process diagram flows smoothly, if manager assigns task to developer, developer reassign the task to manager or completes it. Problem occurs when Manager assigns it to developer A and without reassigning it to Manager if he goes on some vacation. Since Manager can view all the tasks, he assigns the same task to developer B. Now if we check the state of process diagram, it will be in Manager’s task, actually it should be in the ‘Developer to complete Development’ state.
Please help to redesign the process diagram so that it shows the correct states even if manager assigns to developer B.

Probably you can try taskService.setAssignee( taskId, userId ) if your only problem is

Hi Akki,
If I use the above api, task will be assigned to some other developer/user and process diagram will be moved to manager user task, instead it should be in “Developer to complete Development” stage.

For the same post, can someone suggest me how to assign task automatically to the manager, if developer didn’t complete or re-assign the task to manager in some particular period of time.
Thanks in advance.

Will using boundary timer help?