I think Trump understands that a weak yuan and a strong dollar have been bad for US exporters. I don't think he understands much beyond that, either with forex markets, the Fed, deficits, or anything else economically speaking. Like, he says Yellen created a bubble in the stock market. What does he want to do? Repeal Dodd-Frank. He wants to rack up deficits because hey, money's cheap. But if he weakened the dollar, debt would get more expensive. He wants China to free float its currency, but if it did that now, it would probably tank. Etc. etc.