If the pending routing task (listed in the Routing Tab) has sub-tasks associated with it, those sub-tasks will appear in this grid. Then each time a new routing task becomes active, any associated sub-tasks will be added to the grid. Also, any resources associated with the sub-task(s) will be auto-populated in the Resources grid.
Some routing tasks require that all sub-tasks be complete before the routing task can be marked complete. You can close or complete those sub-tasks from the Tasks grid or from the Work Tasks grid in the Routing tab.
To close a sub-task from this grids: