三者的意思没有根本上的区别,都是被说话人明白说话人的语言或行为,如果说硬要区分一下的话,可以从它的语体色彩来分析。
知道,it's a common words, To show that you what people know talk to you
For instance:A: tomorrow you should come here more earlier, and don't be late again
B: okay got it好, 知道了/明白了
知晓 usually used in written language.
她还不知晓这件事的缘由。
晓得we always use it in spoken language, actually, it's more like colloquial words in dialect. According to what i know, it's come from Sichuan.
e.g
A: 你个瓜娃子,晓不晓得上课不能玩儿手机!don't play your phone when you are learning or in your class
B: 噢,晓得咯
OK,I know that
Sorry if i didn't make my answer clear, Cuz you know my English is not good enough.