Tools or tips for calculating fields' contributions to index size

Good day! I’m working on optimizing index storage size and I’d like to learn what APIs are available, if any, for identifying the contributions of individual fields to the overall storage used by an index.

Elasticsearch has the _disk_usage API, is there anything similar in OpenSearch? Does anybody have any tips for specifically identifying areas of improvement for optimizing index disk usage? I’m aware of the Elasticsearch documentation on tuning templates. Thanks!