const k = {
  Age1036: {
    FGB05: {
      'FBG05 06hr 2020': {
        'Section 1': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
        'Section 2': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
      },
      'FBG05 07hr 2020': {
        'Section 1': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
        'Section 2': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
      },
    },
    FGB06: {
      'FBG06 06hr 2020': {
        'Section 1': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
        'Section 2': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
      },
      'FBG06 07hr 2020': {
        'Section 1': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
        'Section 2': [
          'file_example_TIFF_1MB - Copy (2).tiff',
          'file_example_TIFF_1MB - Copy (3).tiff',
          'file_example_TIFF_1MB - Copy (4).tiff',
        ],
      },
    },
  },
};

function getChildren(pathMap, parentPath = '') {
  return Object.entries(pathMap).reduce((acc, [pathName, children]) => {
    const currentDir = {value: parentPath + '/' + pathName, label: pathName};

    if (Array.isArray(children)) {
      currentDir.children = children.map((fileName) => ({value: parentPath + '/' + fileName, label: fileName}));
    } else {
      currentDir.children = getChildren(children, parentPath + '/' + pathName);
    }

    acc.push(currentDir);
    return acc;
  }, []);
}

l = getChildren(k);

m = JSON.stringify(l, null, 2);
m;