GetAsBeautifiedString() expression returns a portion of JSON as a string, which contains key names and values, with quotation marks "" and line breaks. These special characters need to be escaped with "\" if you want to store them in JSON as a string.
To be honest, I don't understand what you are trying to do. If you want to copy all values from "Equip.0" into "Item", use Set JSON action:
JSON Set JSON: "Item" to JSON.GetAsCompactString("Equip.0")