In this dialog it is possible to enter a value without creating a new property. But this has no effect and does not fire an error. I have tried 10 times until I got it…
And two month later the same procedure again. Of course.
Very confusing.
Yes, we are aware and and working on reworking the dialog to optimize it for various use cases. However, I cannot yet promise any date when that will be ready.
Hope is al we need 
I fixed at least the edibility for now.