Hmm problem is that MC does not have much of control over what is added there
MC creates a Popup Menu. Then tells the Windows to fill it with items. according to the list of file items that are also sent to it.
Since there is a reg hack to add this to Windows Explorer. It might be that explorer is also adding this manual to the list. and not via the shell context menu system.
MC might be able to too that. But then it will be under the MultiCommander menu. But currently I have no idea how to do that 'manually'