Using the mobile app I can only see the last course uploaded to the watch. It appears the course that was already loaded on the watch gets overwritten or deleted.
Not sure if related but cannot upload any course .gpx format to the watch via Garmin connect either. Gets to about 90% then I get the following error:
An error occurred with your upload. Please try again.
Can work with this however others have advised they can store up to 10 courses on their device.