// примерная структура
const items = [
  {
    _path: [0],
    title: "[0]",
    children:[
      {
        _path: [0,0],
        title: "[0,0]",
        children: []
      },
      {
        _path: [0,1],
        title: "[0,1]",
        children: [
          {
            _path: [0,1,0],
            title: "[0,1,0]",
            children: [/* ... */]
          }
        ]
      },
    ]
  },
  /* ... */
]

function getElement(tree, path) {
   return getElement(tree[path.shift()].children, path);
}