Entering my start location, right clicking on an alternative direction, the deep blue line follows my choice. Can do that a couple of times, but it always reverts back to a default route.
iMac, macOS High Sierra (10.13.6)
This is crazy, but I found a solution myself.
Enter your start point in the top left box. Using right hand click, click ' GET DIRECTIONS ' along the route you wish to take, - being aware MAPS is going to revert to default at some point - so do be observant of where you are on your route. Take a note of the point where MAPS does revert. Now, repeat the process of routing, but before you reach the point MAPS is going to revert, click SHARE and send it to your phone. Then enter THAT place into the start point and continue planning your route. The route is now saved to the phone and can be used anytime. This is ideal if there are many routes to one destination and you want to go one way, but return another, or use different routes on different occasions. I don't know if this procedure works with the app on the actual phone.
How do I create alternate route in MAPS
