Layer ID

A layer is what the web app calls a group: a set of areas (type area) or points (type point) in a map. You need the Map ID to list them.

To list the area groups of a map, with their areas (reference):

curl 'https://app-api.geposit.se/v2.0/layer/map/{map_id}/area?with_geo_names=true' \
  --header 'x-api-key: {API_KEY}'

Use point instead of area for point groups.

{
  "layers": [
    {
      "layer": {
        "id": "LAYER_ID",
        "map_id": "MAP_ID",
        "name": "North",
        "type": "area",
        "is_hidden": false
      },
      "container": [
        {
          "id": "CONTAINER_ID",
          "layer_id": "LAYER_ID",
          "name": "Arvidsjaur",
          "geo_ids_ref_groups": [],
          "area_sq.km": 1323.3
        }
      ]
    }
  ]
}

(Shortened.) layer.id is the layer ID, and container lists the group's areas, so this call also gives you the Container IDs.