Unable to assign json payload with parameters to a variable

One of our requirements is to parameterize the values in the JSON payload and able to achieve the same when used a smaller payload, In our case the payload is too huge with almost 12000 lines, Unable to parameterize even the single value field

Hi @mokamran, thank you for contacting us. We need a small clarification, is this a product feature you are missing or a bug fix you would like us to resolve? Also a version you are currently using and a screenshot would be very helpful as well.