I know your support for windows mobile hasn't been really great so far, but I still wanted to create a bug report.

What I did,
I downloaded a mcpack, and a mcworld file and was trying to import them when tapping on them in the file explorer.

What I expected,
Minecraft PE should open and should load the mcpack

What happened,
Just a message popped up that I should search in the store for an application for this file extension.

Theory,
The file extensions mcpack and mcworld aren't assigned to minecraft pe on windows phone.

Device: Lumia 640 XL DS, 650, 920, 720. Everywhere the same problem.