Embedded QWindow does not deliver key shortcuts under macOS

We are embedding a QWindow into a native foreign host window, expecting the QWindow to allow event processing at a similar level as a standalone window, especially also in regards to key event processing.

Currently, due to a missing related implementation, key events are only arriving for single keys, but not for key combinations (or how macOS calls these "key equivalents"). As we rely on such key combinations to be available in the QWindow for text editing, these are a substantial part of the provided key handling functionality.

What we would like to have, is the functionality which would be resulting, if the attached patch would be applied. It is understandable that this patch might not be the all-encompassing solution, but it should show-case, how we would expect the key events  to arrive in a minimal embedded plugin-application.

FYI - I was made aware that this is related to the following ticket: https://bugreports.qt.io/browse/QTBUG-71484

Maybe it could be possible - and to get some progress - to try to make the minimal focussed use case work, while not touching any non-plugin-application scenarios yet (which seem very complex on their own).