With the GC app you can only create roundtrips on the phone. They recently added the ability to create point-2-point in GC web.
I use Komoot to create on phone route and deliver them the to watch/edge using the komoot on device app.
May I invite you to use the Contact Support option at the following link rather than post a 1 star review on the Connect IQ page http://help.komoot.de/
You can do this using our routeCourse Connect IQ app -- just create the new route on your mobile browser using our Planner then the routeCourse app on your Edge 520 Plus will download it. More info at https://dynamic.watch/help/routecourse#edgeapp You can do all that with the free version BTW, no need for Premium.
I'll have to try it again, but I paid for premium and have the Dynamic Watch app on my phone and it would just hang while trying to send it to my 520 Plus from my phone. I didn't try opening the routeCourse app on the 520 Plus.