const r = await mn.api('/library/folders?path=');
mn.log(r);

{
  "bridgeApiVersion": "0.91",
  "next": "Folders are plain directories under MarginNote's Documents. \"\" is the root. A document's folder is independent of which study sets reference it — moving it between folders does not break those links.",
  "root": "",
  "depth": 3,
  "folders": [
    {
      "path": "ChatMemories",
      "name": "ChatMemories",
      "depth": 1
    },
    {
      "path": "ImmersiveTemplates",
      "name": "ImmersiveTemplates",
      "depth": 1
    },
    {
      "path": "Imported Pages",
      "name": "Imported Pages",
      "depth": 1
    },
    {
      "path": "ImportEverythingExports",
      "name": "ImportEverythingExports",
      "depth": 1
    },
    {
      "path": "QuizPort",
      "name": "QuizPort",
      "depth": 1
    },
    {
      "path": "TemplateSamples",
      "name": "TemplateSamples",
      "depth": 1
    },
    {
      "path": "ImportEverythingExports/BilibiliVideos",
      "name": "BilibiliVideos",
      "depth": 2
    },
    {
      "path": "TemplateSamples/mn.guide",
      "name": "mn.guide",
      "depth": 2
    },
    {
      "path": "TemplateSamples/u-exam-card-practice",
      "name": "u-exam-card-practice",
      "depth": 2
    },
    {
      "path": "TemplateSamples/u-vocab-reader",
      "name": "u-vocab-reader",
      "depth": 2
    }
  ]
}