.yet the human instrumentalities,working just as they do,are of the best adaptation to effect his purpose.不过人这种工具,虽说我行我素,却能完全领悟上帝的旨意并满足上帝的宏愿.这里的working just as they do翻译成我行我素?是个什么语法结构?

working明明是伴随状语。
“就按照它们事实上工作的方式工作”，do指代work，这句话好像是句废话，只是为了强调，英语里经常这样说。
“我行我素”只是意译，只能说英翻中的时候，反过来用汉语中的意思往英语上套就不是那么回事了。

你可以把句子整理下：working just as they do, the human instrumentalities are of the best adaptation to effect his purpose.这样就清楚了，能理解吗？

working just as they do 是现在分词作后置定语，修饰 the human instrumentalities，在语法上等同于定语从句 which work just as they do。work as they do 直译是：在他们做事的时候就起作用了，意译成了“我行我素”。

它充当伴随状语，修饰前面的名词。这句话若直译的话，意为只按自己意愿做事，这不和我行我素意思差不多吗，但我行我素比它简洁、明了。因此会用它吧。

yet 句首的副词 作状语
the human instrumentalities做主语
working just as they do现代分词做伴随状语
are of the best adaptation to effect his purpose 系动词are表明这后面的是表语 of+名词或名词结构可以当作是形容词 the best adaptationto effect his purpose 就是个名词结构
working just as they do 现代分词做伴随状语