Additionally, you can do simple ad-hoc routing on the watch itself, while you're out on the trail, also totally offline.

For more complex ad-hoc routing, it can be easier to design a route on the Garmin Explore app on your phone and then sync it to your watch via Bluetooth. This works (also totally offline), but the problem is that Garmin Explore's UI and trail labeling kind of sucks, at least on iOS.

My preferred approach, if I'm out on a hike and want to set a new route to someplace, is to draw routes on Gaia GPS (which also has offline maps), then sync them to my Fenix 7 over Bluetooth for navigation. I wrote a Pythonista script to make this work well on iOS: https://github.com/mshroyer/pythonista-scripts/tree/master/G...