That is, you are talking other things other entities might not know about me that I know myself which makes them, from my point of reference, known knowns. And in the event that I don't know those things myself they just become unknown unknowns.
If you don't change goalposts and keep the point of reference constant, unknown knowns wouldn't exist.
Personally, if I actually had to define unknown known from the individual entity's point of reference it would most probably refer to derived or calculated values. For example, do I know the product of 171 and 342.45673. Do I know I could calculate it? Yes. But do I know it by head? No. Which means it is eventually a known but right now it's still unknown. But even that is a stretch of a definition.
I am convinced Rumsfeld's initial proposition covers the entire space of knowledge. Maybe you could give actual examples of unknown knowns from the individual's perspective.
"I apparently know how to parallel park - I didn't know I could do that". And other stuff like it. "Oh, I could manage this project, never thought I'd manage."
The stuff in our brains not immediately accessible to our conscious thoughts. But OP didn't go there which surprised me.
Edit: and from a completely different realm, sadly - why is the baby not moving?
To the other person/parents they don't know that you know, but that's looking at knowledge of party a vs. party b, which is mot quite what all this is about. Yo your parents it's still a known unknown (hence why they ask you).
I believe the closest to unknown knowns would be temporary loss of knowledge, where at a given moment you don't manage to make the right connections between the known knowns. So it's a "could know" given the right moment or prerequisite calculation step/thought, but right there you don't so it's an unknown known.
Biases could also be unknown knowns.
Gary Bernhardt uses this in his "Ideology"[1] talk.
Unknown knowns is not a sensitive category by default, though it can be triggering uncovering painful weaknesses.
I'm not sure I follow what you mean by "unknown knows". How is a sensitive question an unknown known?
Put differently, answers in that quadrant are the ones the questioned individual would like to avoid. As long as you, the asker, avoid asking them, there is a peaceful equilibrium. Once you ask such, you become a hostile.
Or put in the original context - Unknowns Knowns are coverups.
Most of the time it is also possible to deduce it partially. (but careful about that) Unless it is something very unusual.
That's an interesting interpretation, though with a rather negative connotation.
I've also seen it described as unconscious competence, or the highest level of competence -- effortless mastery.
Former Secretary of Defense for two presidents Donald Rumsfeld once framed (brilliantly actually) the possible things we know.
... there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns - the ones we don't know we don't know [1]
A while after someone (which I can’t trace back) made an interesting (and equally brilliant) observation - there is a fourth option - unknown knowns - that is, things we don’t know we know. In most cases, that person pointed out, the category contains, things we actually know, but prefer to pretend that we don’t.
So, what is a sensitive question?
A sensitive question is one for which the answer is an unknown known.
The cost of asking such a question in American society (and, obviously in SV) is dear. Avoiding them is free.
Ask carefully.
[1] https://youtu.be/REWeBzGuzCc