- What a row would there have been if they had known you were here!
- How great would have been her disappointment if she had known what they had actually thought! (Both are example sentences from The Cambridge grammar of the English language, without context)
In (1), how do you interpret "were"？ Does the sentence imply you are here now or is it talking about a past situation?
In (2), does "had" indicate "thought" is anterior to her knowing or to the time of utterance.
I think the two questions are related, so I ask them in the same thread.