The Bin column is blank in the Secondary Index list under the Definitions tab while using the newest server 3.7.0.2.
I reviewed the server code in the secondary_index.c, in as_sindex_list_str function,
the response string changed from the bins to bin in json data.
{"cluster_status": "on", "indexes": [{“bin”: “p_0”, "sync_state": "synced", "set": "metric_tags", "indexname": "Index_0", "indextype": "NONE", "node_status": "on", "state": "RW", "path": "p_0", "ns": "youzan-ldt", "type": "NUMERIC"}]}