In some cases, when submitting a request with a certain pattern, console inserts a line break under the water which breaks the request, without a hint to the user as to why that has happened. Here's a snippet to reproduce:

PUT _ingest/pipeline/entities-v1-latest-builtin_data_streams
{
  "processors": [
    {
      "set": {
        "field": "entity.displayName",
        "value": "{{remote}}{{data_stream.type}}-{{data_stream.dataset}}-{{data_stream.namespace}}"
      }
    }
  ]
}

The issue is with {{remote}}{{data_stream.type}}. If that is changed to {{remote}}-{{data_stream.type}}, the request works again.