You can copy multiple tracks in the route editor on MyRoute-app together, but you have to make them into a route.
If you open one of the tracks as a route and click on the left where it says tracks, you can click on 'add'.
Here you will find all the tracks you have created.
I have added the bug to the list of the developers, many thanks for making this known to us. With the upcoming update the problem should be resolved.
I will now close the forumpost to ensure that there will be no reactions by other users with problems or suggestions not related to the original post.
Customer Support MyRoute-app