How to set the queue size of notification?

After checking and searching, i found this ble_gatts_conn_cfg_t::hvn_tx_queue_size should be the key to set it. In my custom project (SD132 V5 + SDK14.1) the only setting related to this configuration is BLE_GATTS_HVN_TX_QUEUE_SIZE_DEFAULT 1 which is located in "ble_gatts.h".

I dont think i should change the default value in this header. In throughtput example, I couldnt find the codes that related of it.

So how to set the queue size up other than change it directly in the "ble_gatts.h"?