Yes it is straightforward. Create your route as a list of waypoints. I used gpx studio, which normally creates a route of thousands of points, but I got it to cut down to about 8.
The route was then emailed to my phone. The app opened automatically when I accessed the file, showing a "straight lines" preview between the points in the "Route Import" screen.
Opening the route converted it from straight lines between the points to wriggly lines following the roads.