GRouteLoaderIQ is an app that lets you download course and location files from appropriately-configured websites. It wouldn't be too hard to create your own website to download course files from.
You can also use it instead of the gimporter IQ app to access the website gimporter's companion Android app (gexporter) creates.
More info here:
https://www.btcnj.com/mywcc/download.php?file=/downloads/GRouteLoaderIQ.pdf
GRouteLoaderIQ
https://apps.garmin.com/en-US/apps/f03dbbbc-c4b8-4da8-af9c-f262af8c2d0e
gimporter
https://apps.garmin.com/en-US/apps/de11adc4-fdbb-40b5-86ac-7f93b47ea5bb