Grouping nested fileds instead of creating new fields

I used kibana and elastic v7.13.3,
I want my nested fields put inner outer filed in json format instead of creating seperate field for each of them.

"fields.ExceptionDetail.ValidationResultModel.Errors.Message.keyword": ["'Id' must be greater than '0'."],
"fields.ExceptionDetail.TargetSite.keyword": ["Void MoveNext()"],
    "exceptions.Message.keyword": [
      "Exception of type 'BuildingBlocks.Validation.ValidationException' was thrown."
"fields.ExceptionDetail.Type.keyword": ["BuildingBlocks.Validation.ValidationException"],
"fields.ExceptionDetail.HResult": [-2146233088],


I expect all of them to be in the same ExceptionDetail field, as some nested element of this field