does anyone know how to change the default values of dimension field spec values in pinot?

You can set default null values like this:

"dimensionFieldSpecs": [
    {
      "dataType": "BOOLEAN",
      "name": "newBooleanSVDimension",
      "defaultNullValue": "false"
    },
    {
      "dataType": "STRING",
      "name": "newStringMVDimension",
      "singleValueField": false,
      "defaultNullValue": "notSameLength"
    }
  ]

@Mark Needham thank you