{
"participants": [
    {
      "name": "xxxx"
    },
    {
      "name": "xxxx"
    }
  ],
  "messages": [
    {
      "sender_name": "xxxx",
      "timestamp_ms": 1xxxx,
      "content": "xxxx",
      "type": "xxxx"
    },
    {
      "sender_name": "xxxx",
      "timestamp_ms": xxxx,
      "content": "xxxx",
      "type": "xxxx"
    }
 ],
  "title": "xxxx",
  "is_still_participant": xxxx,
  "thread_type": "xxxx",
  "thread_path": "xxxxx"
}

psql
select ab.value, tb.messagenumber, message:: json ->> 'title' as title
FROM public.ImportTable as tb, json_array_elements(message:: json ->
'messages') as ab

Message array 1 | MessageID 1|Title 1
Message array 2 | MessageID 1|Title 1
Message array 3 | MessageID 1|Title 1
Message array 4 | MessageID 1|Title 1
Message array 1 | MessageID 2|Title 2
Message array 2 | MessageID 2|Title 2

psql
SELECT * FROM public.jsonmessage as tb, json_each_text(Message array::
json)