Sorry to go on...
I have worked out that the "extra keys" are taken from the first row.
I am trying to use the Avatar column type. I'm not sure if this expecting a bit too much?
I can see the setting for image and fallback text, but I would like to be able to set the caption, Option list, (colour and icon?), and Status indicator (and options: colour, label, icon, tooltip)?
Perhaps a feature request for a future update?