How can you have multiple levels in an axis in vega-lite?

Is it possible in Vega-Lite to have multiple (hierarchical) facets of a dimension on one axis or would that require Vega?

Best result I found so far was concatenating the information, which is effective but way less appealing:

If I create row-facets, two problems arise: 1) I cannot nest facets, therefore this does not work for 3 or more aspects. 2) all labels are repeated even if there's no data, eg Copenhagen, Apples, Thin Air in the example.

Solution

As suggested, using hconcat provided a (somewhate convoluted) solution combined with lag in aggregate.

Example: like this

{
  "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
  "data": {
    "values": [
      {
        "BI_City": "Amsterdam",
        "BI_Sector": "Cars",
        ...
        etc
        ...
        "Source": "Thin air",
        "Start": "2015-01-01",
        "End": "2019-01-01"
      }
    ]
  },
  "hconcat": [
    {
      "transform": [
        {"aggregate": [], "groupby": ["BI_City", "BI_Sector", "Source"]},
        {
          "window": [
            {"op": "row_number", "as": "rownum"},
            {"op": "lag", "field": "BI_City", "as": "prevCity"},
            {"op": "lag", "field": "BI_Sector", "as": "prevSector"}
          ],
          "sort": [
            {"field": "BI_City"},
            {"field": "BI_Sector"},
            {"field": "Source"}
          ]
        },
        {
          "calculate": "join([datum.rownum, datum.BI_City, datum.BI_Sector, datum.Source, datum.prevCity, datum.prevSector], '|')",
          "as": "rowkey"
        }
      ],
      "height": 500,
      "mark": {"type": "bar", "tooltip": false, "color": "transparent"},
      "encoding": {
        "y": {
          "field": "rowkey",
          "sort": {"field": "rownum"},
          "title": null,
          "axis": {
            "domain": false,
            "grid": false,
            "ticks": false,
            "labelExpr": "split(datum.label, '|')[1] == split(datum.label, '|')[4] ? '' : split(datum.label, '|')[1]"
          }
        }
      }
    },
    {
      "transform": [
        {"aggregate": [], "groupby": ["BI_City", "BI_Sector", "Source"]},
        {
          "window": [
            {"op": "row_number", "as": "rownum"},
            {"op": "lag", "field": "BI_City", "as": "prevCity"},
            {"op": "lag", "field": "BI_Sector", "as": "prevSector"}
          ],
          "sort": [
            {"field": "BI_City"},
            {"field": "BI_Sector"},
            {"field": "Source"}
          ]
        },
        {
          "calculate": "join([datum.rownum, datum.BI_City, datum.BI_Sector, datum.Source, datum.prevCity, datum.prevSector], '|')",
          "as": "rowkey"
        }
      ],
      "height": 500,
      "mark": {"type": "bar", "tooltip": false, "color": "transparent"},
      "encoding": {
        "y": {
          "field": "rowkey",
          "sort": {"field": "rownum"},
          "title": null,
          "axis": {
            "domain": false,
            "ticks": false,
            "labelExpr": "split(datum.label, '|')[1] == split(datum.label, '|')[4] && split(datum.label, '|')[2] == split(datum.label, '|')[5] ? '' : split(datum.label, '|')[2]"
          }
        }
      }
    },
    {
      "transform": [
        {"aggregate": [], "groupby": ["BI_City", "BI_Sector", "Source"]},
        {
          "window": [
            {"op": "row_number", "as": "rownum"},
            {"op": "lag", "field": "BI_City", "as": "prevCity"},
            {"op": "lag", "field": "BI_Sector", "as": "prevSector"}
          ],
          "sort": [
            {"field": "BI_City"},
            {"field": "BI_Sector"},
            {"field": "Source"}
          ]
        },
        {
          "calculate": "join([datum.rownum, datum.BI_City, datum.BI_Sector, datum.Source, datum.prevCity, datum.prevSector], '|')",
          "as": "rowkey"
        }
      ],
      "height": 500,
      "mark": {"type": "bar", "tooltip": false, "color": "transparent"},
      "encoding": {
        "y": {
          "field": "rowkey",
          "sort": {"field": "rownum"},
          "title": null,
          "axis": {
            "domain": false,
            "ticks": false,
            "labelExpr": "split(datum.label, '|')[3]"
          }
        }
      }
    },
    {
      "width": 800,
      "height": 500,
      "transform": [
        {
          "calculate": "join([datum.BI_City,datum.BI_Sector,datum.Source],'|')",
          "as": "rowkey"
        }
      ],
      "mark": {
        "type": "bar",
        "height": {"band": 0.5},
        "stroke": "black",
        "strokeWidth": 0.3
      },
      "encoding": {
        "y": {
          "field": "rowkey",
          "sort": "ascending",
          "axis": {"grid": true, "tickBand": "extent", "labels": false},
          "title": null
        },
        "x": {
          "field": "Start",
          "type": "temporal",
          "axis": {"grid": false, "title": "Year"}
        },
        "x2": {"field": "End"}
      }
    }
  ],
  "config": {
    "concat": {"spacing": 0},
    "view": {"fill": "transparent", "stroke": null}
  }
}