$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()

Add-Type -Path "C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions16ISAPIMicrosoft.SharePoint.Client.dll"
Add-Type -Path "C:Program FilesCommon FilesMicrosoft SharedWeb Server Extensions16ISAPIMicrosoft.SharePoint.Client.Runtime.dll"


Function Get-SPOContext([string]$Url,[string]$UserName,[string]$Password)
{
   $context = New-Object Microsoft.SharePoint.Client.ClientContext($Url)
   $SecurePassword = $Password | ConvertTo-SecureString -AsPlainText -Force
   $credentials = New-Object Microsoft.SharePoint.Client.SharePointOnlineCredentials($UserName, $SecurePassword)
   $context.Credentials = $credentials
   return $context
}


Function FindNavigationNodeByTitle([Microsoft.SharePoint.Client.NavigationNodeCollection]$Nodes,[string]$Title)
{
      $context = $Nodes.Context
      $context.Load($Nodes)
      $context.ExecuteQuery()
      $node = $Nodes | Where-Object { $_.Title -eq $Title }
      return $node
}


Function AddNavigationNode([Microsoft.SharePoint.Client.NavigationNodeCollection]$Nodes,[string]$Title,[string]$Url){
   $context = $Nodes.Context
   $Node = New-Object Microsoft.SharePoint.Client.NavigationNodeCreationInformation
   $Node.Title = $Title
   $Node.Url = $Url
   $Node.AsLastNode = $true
   $context.Load($Nodes.Add($Node))
   $context.ExecuteQuery()
}







$tenantUrl = "https://tenant.sharepoint.com/"
$userName = "username@tenant.onmicrosoft.com"
$password = "password"



$Context = Get-SPOContext -Url $tenantUrl -UserName $userName -Password $password

#$NavBar = GetTopNavBar -Context $Context
$NavBar = $Context.Web.Navigation.TopNavigationBar
$Context.Load($NavBar)
$Context.ExecuteQuery()


$parentNode = FindNavigationNodeByTitle -Nodes $NavBar -Title "Hello"

if($parentNode) {
   $Context.Load($parentNode.Children)
   $Context.ExecuteQuery()
   AddNavigationNode -Context $Nodes $parentNode.Children -Title "Tasks" -Url "/Lists/Tasks/AllItems.aspx"
}

$Context.Dispose()