How do I define my own JSON Schema keyword and vocabulary?

I would like to define a JSON schema vocabulary to extend any regular JSON schema with storage related metadata. As an example I would like to define a pk keyword which marks an arbitrary JSON property as a primary key.

My meta-schema looks like this:

{
  "$schema": "http://json-schema.org/draft/2019-09/schema#",
  "$id": "https://myschema/meta/storage-schema",
  "$vocabulary": {
    "https://json-schema.org/draft/2019-09/vocab/core": true,
    "https://json-schema.org/draft/2019-09/vocab/applicator": true,
    "https://json-schema.org/draft/2019-09/vocab/validation": true,
    "https://json-schema.org/draft/2019-09/vocab/meta-data": true,
    "https://json-schema.org/draft/2019-09/vocab/format": false,
    "https://json-schema.org/draft/2019-09/vocab/content": true,
    "https://myschema/vocab/storage-schema": false
  },
  "$recursiveAnchor": true,

  "title": "JSON Storage-Schema",
  "allOf": [
    {"$ref": "https://json-schema.org/draft/2019-09/schema"},
    {
      "$recursiveAnchor": true,

      "title": "storage vocabulary meta-schema",

      "type": ["object", "boolean"],
      "properties": {
        "pk": {
          "description": "Marks a property as primary key",
          "type": "boolean",
          "default": false
        }
      }
    }
  ]
}

And a corresponding JSON instance might be:

{
  "$id": "https://myschema/invoice.schema.json",
  "$schema": "https://myschema/meta/storage-schema",
  "type": "object",
  "properties": {
    "invoiceNumber": {
      "pk": true,
      "type": "string"
    },
    "invoiceIssueDate": {
      "type": "string"
    }
  }
}

However, I am not sure if I am on the right track. For example WebStorm's IntelliSense only offers the pk keyword as a top level keyword and not as a keyword for properties:

{
  "$id": "https://myschema/invoice.schema.json",
  "$schema": "https://myschema/meta/storage-schema",
  "$comment": "Webstorm IntelliSense works and pk documentation is displayed",
  "pk": false,
  "type": "object",
  "properties": {
    "invoiceNumber": {
      "$comment": "No webstorm IntelliSense and no documentation displayed",
      "pk": true,
      "type": "string"
    },
    "invoiceIssueDate": {
      "type": "string"
    }
  }
}

Does anyone have experience with meta-schemas and custom keywords and can confirm if I am doing it right?