請問這句Dorothy could not use it against her, even had she known how to do so為什麼會用倒裝?had she known?

這個超簡易的.一般來說,有使用助動詞的句子倒裝就同等是假設語氣.


Had she known how to do so. = If she had known how to do so.

其他例子們:

We will bring it to them, don't they come here.
= We will bring it to them if they don't come here.

You could get laid too, had you come to the party.
= You could get laid to if you had come to the party.

Call me, should you have any questions.
= Call me, if you should have any questions.

From the Wizard of OZ:-Had she known =If she had known=if they had come=if they don't come here.=the subjunctive mood.