Hi @fahadmicro
Unfortunately, there is no way to do the addition directly in the JSON object editor. But you can use Value Setter to create the property AssignedIdentification_01 and assign it with &{index} as the value.
Then, in the same configuration of the Value Setter, you can add a mapper called “Prepared Operator”. Select “Addition” as the operator and set the “Left” as a number with 1 as the value. Please give it a try.