From https://github.com/open-telemetry/opentelemetry-specification/blob/563958cb2bd8529990f19fdce7a5f3643bf63091/specification/configuration/sdk-environment-variables.md?plain=1#L222:

The SDK MAY accept a comma-separated list to enable setting multiple exporters.

This would be useful, but doesn't really fit with how the package is currently designed.

Originally posted by @dashpole in #4229 (comment)