Since Nx is more or less a replacement for good ol' scripts, I keep its project-specific configuration in package.json:

{
  "name": "foo",
  "nx": {
    "targets": {
      "fun": {
        "executor": "nx:run-commands",
        "options": {
          "command": "rimraf /"
        } 
      }
    }
  }
}

Currently the plugin doesn't check it for configuration:

So Knip errors with:

Unused devDependencies
                   
rimraf              package.json

Just in case, it has the exact same shape as project.json, just one level deeper, under nx.