If they are not windows as defined by the macOS, then KM will not be able to "see" them, or reference them.
The best window discovery tool I know of is further down in the topic you referenced:
So, if the objects you want to access do not appear in that list, then you will have to resort to AppleScript UI scripting, which can access any element on a window. To discover these objects on a window, try this tool, also by @ccstone: