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Well, my answer answers that, check out the posting I linked to. You must insert a MENURESOURCE_SUBTITLE:
menu.InsData(c4d.MENURESOURCE_SUBTITLE, "My Heading")
I just simply add a plugin to C4D which creates a user menu into C4D all in one pack without adding any script into the user C4D preferences folder ( library / scripts ) . Menu and script embedded solution all in one plugin inside.