The first thing I did after installing the beta was to double-click on one of the sample projects. I was then prompted for a file to import (I selected the same file again) and entered a folder to use and pressed the Import button. Nothing happened except an error was reported in red on the screen.
I can see this not the correct way to open an existing app but I can imagine many doing exactly the same because (at least in Windows) the extension is tied to the designer executable.
It may be helpful to head new users in the right direction at this point by, for example, preventing the action or by creating an appropriate new project in the background automatically.