Drop Stops are designed for situations when one Stop (say, Stop A), must happen before another (say, Stop B), but the rest of your Route order can vary. This allows the Route to be optimized within those constraints.
To set up a Drop Stop situation where Stop A must happen before Stop B:
- Add Stop A and Stop B as Stops
- Tap Stop A, and select Set Drop Stop
- Select Stop B from the pop-up list
Then, when you Optimize, Stop A should come before Stop B in your list.