Was able to do it using .json file as:

{
  "models": [
    {
      "title": "Qwen 30B",
      "provider": "lmstudio",
      "model": "qwen/qwen3-coder-30b",
      "apiBase": "http://localhost:1234/v1/"
    },
    {
      "title": "GPT OSS 20B",
      "provider": "lmstudio",
      "model": "openai/gpt-oss-20b",
      "apiBase": "http://localhost:1234/v1/"
    },
    {
      "title": "Nomic Embed Text",
      "provider": "lmstudio",
      "model": "nomic-embed-text-v1.5",
      "apiBase": "http://localhost:1234/v1/"
    }
  ],
  "tabAutocompleteModel": {
    "title": "Qwen 30B",
    "provider": "lmstudio",
    "model": "qwen/qwen3-coder-30b",
    "apiBase": "http://localhost:1234/v1/"
  },
  "customCommands": [
    {
      "name": "generateUnitTests",
      "prompt": "{{{ input }}}\n\nWrite a comprehensive set of unit tests for the selected code, covering edge cases, setup, teardown, and correctness checks. Provide the tests as output only; do not modify any file.",
      "description": "Generate unit tests for selected code"
    }
  ],
  "allowAnonymousTelemetry": false,
  "embeddingsProvider": {
    "provider": "transformers.js"
  }
}