portainer/build/docker-extension/metadata.json

{
  "icon": "portainer.svg",
  "vm": {
    "composefile": "docker-compose.yml",
    "exposes": { "socket": "docker.sock" }
  },
  "ui": {
    "dashboard-tab": {
      "title": "Portainer",
      "root": "/public",
      "src": "index.html"
    }
  }
}