How to Use PowerShell V3.0 and CSOM to add Child Links to the Global Navigation bar in our Online SharePoint 2013

I am stuck on a PowerShell V3.0 problem for programmatically adding Child Links to the Global Navigation bar in our Online SharePoint 2013 (Office 365-Azure) site.

I have found code that works for me to add Headers, to my top link global navigation bar, but I cannot find anywhere, how to add children links under a given header on the global navigation bar. I am using CSOM libraries to do this.

While Googling, everything I have found either uses PS snapins from Sharepoint 2010 (which I cannot download and use in Sharepoint 2013 – unless someone knows of a way to do that), or is written in C# or VB and I am unable translate the code into PowerShell.

Is there any chance that someone would know how or be able to point me to a  resource that would help me solve this issue? The following code snippets work well to add the top level links/headers to the global navigation bar for me but how to add sub links under these headers, programmatically using PowerShell v3.0?

I put the following in a foreach-object loop reading the information from an XML file…this all works well, for adding top level headers/links. I believe I just need to make slight alterations to this code to add sub-links under my global nav headings, but cannot figure out how:

$siteUrl = $_.Url
$siteTitle = $_.Title
$context = New-Object Microsoft.SharePoint.Client.ClientContext($siteUrl)
$context.Credentials = $credentials
$context.RequestTimeOut = 5000 * 60 * 10;
$web = $context.Web
$site = $context.Site
$context.Load($web)
$context.Load($site)
$context.ExecuteQuery() 

$NavBar = $context.Web.Navigation.TopNavigationBar
$NavigationNode = New-Object Microsoft.SharePoint.Client.NavigationNodeCreationInformation
$NavigationNode.Title = $ItemName
$NavigationNode.Url = $ItemUrlPath
$NavigationNode.AsLastNode = $true   
$context.Load($NavBar.Add($NavigationNode))
$context.ExecuteQuery()

gm.ca