0👍
If I understand correctly, you want to type something inside your form and have it updated in your data array.
Assuming your data table library is doing some magic behind the scenes and takes care for the binded property (rate) per each row, then all you should do is deep watch the array of objects and track changed values via some custom code \ small library that track changed values inside an object.
To be more clear, the watch property of Vue is responsible to tell you that there was a change inside some property in your data.
It won’t detect the changed value.
However, inside the detection, you should invoke that custom code \ small lib to differ the value.
I will be more then happy to edit my answer in order to help you with your code once you upload a working sample via: https://stackblitz.com/edit/vue
Currently, this answer operates as a guideline.