It was apparent to me,even at a young age,that wearing the title “mom” was my mother’s most important identity
it 是形式主语
真正主语是 that wearing the title “mom” was my mother’s most important identity
这是一个主语从句,其中wearing the title mom是主语,was是谓语动词
my mother's most important identity是表语.
翻译成:佩戴上妈妈这个头衔是我母亲最重要的身份
(也就是当好母亲,做好母亲的角色)
wearing 是动名词做主语,当然一般说成-ing形式就可以了