How to create nested Tab Groups

For some reason I can't create any nested folders/tab groups in a tab group from within a Script, though the initial creation of a tab group succeeds, and the creation of a child "succeeds", I can get its name and .folder status

  var tabGroups = DOpus.TabGroups;
  var td1 = tabGroups.AddChildFolder('1PrefixDir'); DOpus.Output("td1.folder=" + td1.folder +" name=" + td1.name);
  // also tried with a single save at the end
  tabGroups.Save();
  var td3 = td1.AddChildFolder('PrefixDir2d @ 1PrefixDir'); DOpus.Output("td3.folder=" + td3.folder +" name=" + td3.name);
  tabGroups.Save();

Trying to save to an existing folder also doesn't work

  var tabGroups = DOpus.TabGroups;
  for     (var e = new Enumerator(tabGroups); !e.atEnd(); e.moveNext()) {var tg = e.item();
    if ((tg.folder) && (tg.name === '1PrefixDir')) {
      var td3 = tg.AddChildFolder('PrefixDir2d @ 1PrefixDir');
      tabGroups.Save();
    }
  }

A fix for this was in Directory Opus 13.13.8 (Beta).

Well, now I have the same issue with deleting tab groups in a folder, DeleteChild on a found tab group doesn't delete anything

A fix for deleting will be in 13.14.1.