How to insert nested field?

[Dogrtt]

I'm using otel-collector to push traces from a KongAPI to an ELK APM.
I want to use the Attributes processor to insert field:

"service": {
"environment": "dev"
}

I specified processor:

processors:
attributes:
actions:
- key: service.environment
value: "${env:ENV}"
action: insert

Mentioned it in a pipeline:

service:
pipelines:
traces:
receivers: [otlp]
processors: [batch, attributes, memory_limiter]
exporters: [logging, otlp/elastic]

But in resulting message I'm receiving:

"labels": {
"service_environment": "dev"
}

Why is it going like this?