World Import Button doesn't work

In Minecraft Windows 10 Edition - Clicking "import" and selecting the world doesn't import the world save. See photos attached. It's not clear how the "import" button works or what files are accepted but I have the world save downloaded to my computer. I understand I could just copy my world save to the saves folder in packages but then there wouldn't be a point for the "import" button which should be making the job easier.

EDIT: I browsed the entire directory, plus lower directory db but importing doesn't work for either.