[Solved] How would I approach sorting something like this

Here is how you would do that without using a Treeview (why wouldn’t you I don’t know):

void Main()
{
    string values = @"1
  14
    141
        141010
        141020
        141030
        141040
        141050
        141060
    142
        142010
        142020
    144
       1440
          144010
          144020
          144030
          144040
    145020
    145030
    145010
          ";

    int myValue;
// Splitting and converting to a collection of integers ordered by randomly
// just to show initial order doesn't matter
    var myData = values.Split("\r\n".ToCharArray(), StringSplitOptions.RemoveEmptyEntries)
        .Select(s => int.TryParse(s.Trim(), out myValue) ? myValue : -1)
        .Where(n => n != -1)
        .OrderBy(n => Guid.NewGuid());

// We have the collection. Sort it "directory" style
    List<string> myList = new List<string>();
    var list = myData.Select(d => d.ToString());
    foreach (var v in myData)
    {
        myList.Add(Fullpath(v.ToString(), list));
    }
    var ordered = myList.OrderBy(l => l);
// Write out the result intended
    foreach (var element in ordered)
    {
        var levels = element.Count(e => e == "https://stackoverflow.com/");
        var value = levels > 0 ? element.Remove(0, element.LastIndexOf("https://stackoverflow.com/") + 1) : element;
        Console.WriteLine("".PadLeft(levels, '\t') + value);
    }
}

// Get the full path for a value with ancestors
// ie: 1/14/1440/144010 is the full path for 144010
private string Fullpath(string key, IEnumerable<string> list)
{
    List<string> paths = new List<string>();
    for (int i = 1; i <= key.Length; i++)
    {
        if (list.Any(v => key.Substring(0, i) == v))
        {
            paths.Add(key.Substring(0, i));
        }
    }
    return string.Join("https://stackoverflow.com/", paths);
}

Note that values are shuffled before starting to sort and this is what you get:

1
  14
    141
      141010
      141020
      141030
      141040
      141050
      141060
    142
      142010
      142020
    144
      1440
        144010
        144020
        144030
        144040
    145010
    145020
    145030