APIs that support flat settings are not documented

[advision-digital]

APIs that support flat settings are not documented. I would expect that somewhere support for flat settings is documented for update APIs. One example:

PUT _index_template/debug-template
{
	"composed_of": [],
	"index_patterns": [
		"yyyyyy-*"
	],
	"template": {
		"mappings": {
			"properties": []
		},
		"settings": {
			"index.number_of_shards": 1,
			"index.codec": "default",
			"index.mode": "standard",
			"index.routing_partition_size": 1,
			"index.soft_deletes.retention_lease.period": "12h",
			"index.load_fixed_bitset_filters_eagerly": true,
			"index.shard.check_on_startup": "false",
			"index.number_of_replicas": 1,
			"index.search.idle.after": "30s",
			"index.refresh_interval": "10s",
			"index.max_result_window": 10000,
			"index.max_inner_result_window": 100,
			"index.max_rescore_window": 10000,
			"index.max_docvalue_fields_search": 100,
			"index.max_script_fields": 32,
			"index.max_ngram_diff": 1,
			"index.max_shingle_diff": 3,
			"index.analyze.max_token_count": 10000,
			"index.highlight.max_analyzed_offset": 1000000,
			"index.max_terms_count": 65536,
			"index.max_regex_length": 1000,
			"index.query.default_field": [
				"*"
			],
			"index.routing.allocation.enable": "all",
			"index.routing.rebalance.enable": "all",
			"index.gc_deletes": "60s",
			"index.default_pipeline": "_none",
			"index.final_pipeline": "_none",
			"index.hidden": false
		}
	},
	"version": 1739874433
}