Unreal Engine 4 is available for Win10 UWP app dev now

I was able to create a Certificate but as soon as I start packing I get several warnings “Games/Projects/MyProject/Build\UWP\SigningCertificate.pfx’ error.”
And at the end the packing fails because a problem with the AppxManifest.xml

Working with UWP is horribly frustrating right now. It takes unreasonably long to pack a project which fails in the last steps and there is no clear documentation. Where should I add an Appxmanifest ?!