Managed Assets (app/assets) in IntelliJ IDEA

I facing the problem that managed resources are not properly displayed in the project explorer in IntelliJ IDEA.

Any file which I try to add to the app/assets folder, disappears from the project explorer.

I filed an issue to the Scala plugin issue tracker:
https://youtrack.jetbrains.com/issue/SCL-15482

Was anyone annoyed by this issue?