Is is possible to turn a cycling 'activity' you have recorded, in to a 'course', using the ios phone app?

I can't see how it could be done. There are no controls allowing that as far as I can see. On the web app, there's a gear on the top right corner when displaying an activity that opens a menu containing the "Save as a course" action. The three vertical dots top right on the iOS app open a menu which does *not* include this action, and 'modify the activity' doesn't get you there either.

You are correct. Not possible on the app. You'd have to use the web browser on your phone.

It’s a shame as it would be a useful function to have. I organise the cycle routes for a group of friends and it would be useful to convert a route I have ridden and recorded as an activity, into a course and then WhatsApp it to my group of friends.

Hopefully someone at Garmin is reading this and could get it incorporated into an app update?