Today Garmin announced the Courses API to make it easier to send routes to a GPS: https://garmin2019news.q4web.com/newsroom/press-release-details/2020/Garmin-announces-Garmin-Connect-Courses-API-/default.aspx
The press release is clear that it's an API open to other applications - "The integration will allow users to import their route files created through third-party applications, like Strava and Komoot, and will automatically download to a compatible Garmin device". (Note the word "like" - i.e. not just those two!)
Are there any details of this API anywhere?
(Not strictly Connect IQ, but I couldn't see any other developer forum.)