I wouldn't have troubled him so much if I had known he was so busy.

如果我知道他这么忙，我就不会这么麻烦他了。

youdao

If I had known the exercises should be handed in today, I'd have finished them yesterday.

如果我知道今天要交练习题，我昨天就会把它们做完了。

youdao

'If only I had known you then,' he said wistfully.

“要是我那时认识你就好了。”他向往地说道。

《牛津词典》

I have always known the woman who died in those games had a child.

VOA: special.2010.07.31

And humankind receives its first set of explicit laws, no more implicit, "Murder is bad." "Oh I wish I had known!"

人类要接受明确的律法，而非隐晦的，谋杀是不好的，哦！我要是早知道就好了“

耶鲁公开课 - 旧约导论课程节选

I had known about myself. I'm just interested in women.

我了解自己，我就是对女性感兴趣。

普林斯顿公开课 - 人性课程节选

Here are a few things I wish I had known before I started my company (Part 1).

FORBES: 10 Lessons From an Accidental Entrepreneur (Part 1)

This is an impossible goal to achieve and I wish I had known that when I was 13.

BBC: Jennie Runk: My life as a 'plus-size' model

One of the members of the group was a woman I had known since I was a sophomore in college.

FORBES: How The Peace Movement Failed On 9/11