I found this AnswerHub topic that didn’t get clearly resolved but was marked as answered: No Windows Explorer Context Menu - Platform & Builds - Unreal Engine Forums
The answer was in there, which was to set the default file association to the UnrealVersionSelector.exe in the Launcher install.
So I installed my Launcher from the installer mentioned in #3 above and installed to “c:/program files/unreal engine”. Then I set my MyGame.uproject default program to “F:/Program Files/Unreal Engine/Launcher/Engine/Binaries/Win64/UnrealVersionSelector.exe”. This brought back the context menus and they operate as expected, in that they launch my engine and my editor, not a downloaded engine.