google’s “my maps” is a pretty good resource for planning trips, as you can save maps with locations, routes etc, and then share those maps with others. I’ve used it to for European trips to pre-plan as well as record all the places across the continent we’ve visited and driven. You can then view those maps overlaid into google maps app on your phone, but so far as I know you can’t use those as active navigation but I am wondering of you can add a route on “my maps” which comes up as a blue line, and then view that blue line on your phone. It won’t give you directions but it would be possible to just follow the line. I need to experiment a bit with that!