Layout is:

[tool.newrelic]
app_name = "app name"

Keys with . in them are expanded to be subkeys:

[tool.newrelic.browser_monitoring]
enabled = true

Anything that is a list in the layout is made into a string joined with a single space.

import-hook: is translated as such:

[tool.newrelic.import-hook.module_name]
"sub.sub" = ["item1", "item2"]

error_collector.ignore_errors:

[tool.newrelic.error_collector]
ignore_errors = ["module.name:ClassName", "module.name:ClassName2"]

Environment use the tool.newrelic.env namespace:

[tool.newrelic.env.production]
app_name = "production name"