Thanks for the feedback, @Kelapa. The migration process via shared folders has indeed never been optimal, a situation which is happily about to improve.
You might’ve seen elsewhere in the forum that we have a new extension and web-app currently in beta (click to sign up); besides many other new features already being tested it will also soon include a completely new sharing structure and the ability to just switch the associated email without any workarounds.
We are working hard to implement the missing new features and roll out more publicly by summer, so there will be more news on this front soon.