Shell Extensions, such as Context Menu Handlers have been sought after in MSIX for quite a while. While the Microsoft MSIX Packaging Tool does not support them (today), there is plenty of evidence from Microsoft that they should be possible.
which shows an example. (The example is clearly incorrect, as the Application element required an Id attribute and VisualElements subnode. While an older example, it is not deprecated and it is not uncommon for desktop bridge documentation to be referenced for MSIX, even if not perfect. Even through shell extensions don't necessarily tie to an exe inside the package when implemented as an in-process com object in the file explorer, we can usually find an application in the package to leverage to overcome this).
It does not seem possible to get this example (nor any other) to work. Can we get some feedback on the status of shell extensions? Is it that:
There are gaps in the documentation that need addressing but they work if specified correctly.
It is supposed to be working, but there are bugs in the implementation (AppInstaller and or runtime) that need fixing.
Microsoft is still working on a complete implementation and customers should be patient.
Microsoft has decided not to support the functionality going forward.