The plugin defaults to the Rust tracing_subscriber::fmt::json layout. For other log libraries, change these five paths under Settings → Tools → JSONL Log Viewer → Field mapping. Paths are dot-separated JSON lookups (fields.message means “look up fields, then message”); empty path disables that semantic slot.

Format	Timestamp	Level	Target	Message	Fields container
Rust tracing (default)	timestamp	level	target	fields.message	fields
pino	time	level	name	msg	(blank)
Serilog	@t	@l	SourceContext	@mt	(blank)
bunyan	time	level	name	msg	(blank)
OpenTelemetry Logs	timestamp	severityText	attributes.code.namespace	body	attributes

When fields container is blank, every top-level JSON key that isn’t consumed by the other four paths is rendered as a key=value pair. When it’s set, only keys under that object are rendered, with the leaf consumed by message suppressed so you don’t see the message duplicated.