I've been using the course Navigation on the watch to run some unfamiliar trails. I came from a Polar watch that used Komoot, which IMO had a good, streamlined implementation of the course navigation.
There are a few small usability issues that I think could be tweaked:
Autozoom - it is hard to judge the location of a turn when this feature is enabled - since the scale can change. Most of the time, I find the default level to be too zoomed out to help deconflict trail intersections. I end up disabling this feature and using the manual setting, which keeps resetting its zoom level on every run. It would be great if this just remembered the last zoom setting and kept it there for the next time.
Visibility - the lines could be thicker - to compensate for this, I have had to turn the backlight on for the trail activity. Using a thicker line to render the course would really improve visibility, especially when one is under the tree canopy.
Sounds - I think the sound for an upcoming turn should be different from the off-course warning.
My guess is that these issues have probably been present since the Fenix 3 days. IMO, a lot of development resources have been devoted to maps - which are usable by some people, and are a selling point for other Garmin watches. But I know I'm not the only trail runner that wants to compose a route before hand, and wants a clean, easy to read navigational aid. A full map display can (at times) be overly complex to read when bouncing down the trail.
Thanks for reading.