hass-config/.storage/timer

{
  "version": 1,
  "minor_version": 1,
  "key": "timer",
  "data": {
    "items": [
      {
        "name": "Countdown 1",
        "icon": "mdi:timer",
        "restore": false,
        "duration": "0:00:00",
        "id": "countdown_1"
      }
    ]
  }
}