All of the values in the selected JSON column are combined into a single JSON structure and written to a file. Depending on the Place resulting JSON setting, the combined rows are either placed Under root key (as the value of that key) or At top level in the file. You can use Additional properties to add custom key/value pairs next to the combined JSON. The Combine rows as option controls whether the rows are collected into an Array or into an Object with key (using a key column to name each entry). (The JSON content in the file can be pretty-printed.) For example, when combining rows as an array under a root key with additional properties, the output looks like this:
{
"JSON key": [
{ "json": "from Row1" },
{ "json": "from Row2" }
],
"custom key": "custom value"
}