Export-AadHeirarchy.ps1

[CmdletBinding()]
param
(
    [Parameter()]
    [String[]]
    $StartingUsers,

    [Parameter()]
    [bool]
    $EnabledUsersOnly = $true
)

$upnsToLookup = New-Object System.Collections.Stack
$StartingUsers | `
    ForEach-Object {
        $upnsToLookup.Push($_)
    }

$usersFound = New-Object System.Collections.Generic.List[PSObject]

$upnsToLookup | `
    ForEach-Object {
        $user = Get-AzureADUser -SearchString $_
        $usersFound.Add($user)
    }

do {
    $nextLookup = $upnsToLookup.Pop()
    $result = Get-AzureADUserDirectReport -ObjectId $nextLookup | `
        Where-Object { $_.UserType -eq 'Member' }
    if ($EnabledUsersOnly) {
        $result = $result | Where-Object { $_.AccountEnabled }
    }
    $result | ForEach-Object {
        $upnsToLookup.Push($_.UserPrincipalName)
        $usersFound.Add($_)
    }
    Write-Progress -Activity "$($upnsToLookup.Count) lookups in queue; $($usersFound.Count) users found"
} while ($upnsToLookup.Count -gt 0)

$usersFound | Sort-Object -Unique -Property UserPrincipalName