Feature description

An arborescent data editor should be added to QGIS for the unfolding of the full potential of GeoJSON.
One should also be able to map visuals to deep GeoJSON "property" objects. Example: the label editor in layer properties should be able to use an expression like concat("name.en",' (',"name.local",')') to construct labels.

Additional context

Graph databases exist since 2000 but we are still using flat table models to store and edit geodata in GIS solutions. We should move on and stop wandering in NULL fields.

Wouldn't GeoJSON be an excellent format for storing and editing deeply arborescent data?

It has more potential than a flat table with a WKT field currently used by GeoPackage. To use the full potential of the GeoJSON object-oriented format, an appropriate editor should be added to QGIS. Here an example of such an editor by @josdejong

One should also be able to map visuals to JSON object variables. Example: the label editor in layer properties should be able to use an expression like concat("name.y1491.en",' (',"name.y1491.local",')') to obtain a Constantinople (Κωνσταντινούπολις) label from this GeoJSON layer:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "name":{
          "current":{
            "local":"İstanbul",
            "en":"Istabul"
          },
          "y1491":{
            "local":"Κωνσταντινούπολις",
            "en":"Constantinople"
          }
        }
      },
      "geometry": {
        "type": "Point",
        "coordinates": [
          29.179687499999996,
          40.91351257612758
        ]
      }
    }
  ]
}