getting this Root mapping definition has unsupported parameters: mapper_parsing_exception while running below query in Kibana Console

You need to remove the developer type (between mappings and properties), as types have been deprecated:

  PUT developer
  {
    "mappings": {
      "properties": {
        "name": {
          "type": "text"
        },
        "skills": {
          "type": "object",
          "properties": {
            "language": {
              "type": "keyword"
            },
            "level": {
              "type": "keyword"
            }
          }
        }
      }
    }
  }