Once you've created a route plan, you can still manually move orders from one driver to another. The Route Plan view is divided into two halves. The top half shows a map with your orders pinned on it while the bottom half displays a gantt chart with those same orders displayed chronologically on a timeline (circles are pickups, squares are dropoffs).
Each row (and color) represents the orders to be fulfilled by a single driver. The scheduled arrival time at each pickup and delivery can be found by clicking on the order icon. This brings up an information window showing the order ID, status, customer name and predicted ETA (estimated time of arrival).
Dragging the order icon from one row to another will override the route optimization algorithm and transfer an order from one driver to another. You can make as many transfers as you want.
To save your changes, simply press the [Apply] button on the bottom right. If you want to return the order assignment to what it was before, simply click [Optimize Route].