Navigation - automatic reordering?

That is a lovely restatement of the "traveling salesman problem," which is a classic, and classically difficult, problem in computer science. Take a look at Travelling salesman problem - Wikiwand - do not expect to be able to read and understand that article, because if you have had enough math to understand the article, you surely would have recognized that you have an example of this problem. If you search the Apple appstore or Google Play for "traveling salesman problem," you will find apps under various names that will help you - not necessarily with the perfect solution, but better than you are likely to come up with with pencil and map in any reasonable amount of time. You may be able to transfer your destinations to the Prime's nav screen from your phone, but I would just navigate with the phone.

 

I don't have a Prime, just a Gen 4 Three Touring, but I did notice that upon entering multiple destinations in the Nav, it would show an overview map of the route with the various destinations numbered from 1 to n, and it was fairly easy to spot which ones were out of order. Then you could edit the destinations and reorder them manually as you said. Also, I have owned two dash mount GPS (Garmin and Magellan) that will automatically optimize a route of multiple destinations at the push of a button.

 

One problem that I have run into with many GPS is when you have a route with multiple stops, when you reach one of the stops you may not hit the exact "target", especially at a business where you come in on a different driveway than it expected. Then when you drive off, following the directions from the GPS, you don't always immediately realize that it is still trying to get you to the previous stop, wasting time until you realize what it is doing. Even when you do realize it, with some GPS it's not always easy to remove a stop from a route, requiring moving through menus, not easy to do if you have already started driving.

I have used a few GPS that are smart enough to figure out that if you pass within say 100 yards of your destination and are now moving away from it, then it automatically removes the previous stop from the route and sends you off to your next one.

Hard to know how a particular GPS will handle this until you have used it. Maybe since the OP is delivering to houses hopefully it won't happen as often, unless for example they park around the corner from one of the houses where they are delivering. If the particular GPS being used doesn't handle these situations well, then you have to get into the habit before leaving a stop to go into the route menu and make sure that it has now moved onto the next stop, and if not then delete the previous stop. I have actually found it better to do all of this when you arrive at each stop prior to turning off the car, which is also a good time to make a mental note of which direction you should head out of the parking lot for your next stop. Otherwise when you later start the car the GPS has to find the satellites again, and also it will have "forgotten" which direction your car is pointing, so unless you staying directionally oriented yourself, you have to start driving in basically a random direction before the GPS figures out which way the car is pointed, at which point it it tells you to do a u-turn because you started out the wrong way. Been there done that a few times.