One of your employees (e.g. John Doe) is no longer working on your company and you want to transfer all Tasks that were assigned to him that are In-Progress and Not Started status to the new employee.
This is possible using the Mass Update feature.
1. Navigate to Lists > Mass Update > Mass Updates
2. Under General Updates, click Task
3. Under Criteria, enter your filters. For example:
Assigned To = is (Employee record of the previous employee John Doe)
Status = Is Any Of In Progress, Not Started
4. Under Mass Update Fields, mark Assigned To and select the new employee e.g. Jane
5. Click Preview
6. After you verified that the results are correct, click Perform Update
This should re-assign all the Task from John Doe to Jane Smith.