According to https://www.microsoft.com/en-us/download/details.aspx?id=35474 to integrate with Office as a cloud provider you need to add a registry entry under HKEY_CURRENT_USER\Software\Microsoft\Of...
Bogdan Mitrache Thanks for your suggestion. I wasn't able to test a modification package (yet).
Did I understand it correctly that I should create a modification package for the Office MSIX.
What I try to achiev is that my application (not office) that is installed via MSIX creates a registry key that Office (no MSIX) will read to display my application as a cloud provider.
If I understand the modification package correctly, it will add the registry keys to the context of my app, but not globally.