FunctionsPublic/New-GraphFolderInGroup.ps1

function New-GraphFolderInGroup
{
    param([psobject]$accessToken, [string]$groupID, [string]$parentItemID, [string]$folderName)
    #
    # Create new unified group
    #
    $sendBody = @{
        "name" = "$($folderName)";
        "folder" = @{}
        } | ConvertTo-Json 
    $sendBody

    $responseBody = Invoke-RestMethod `
        -Uri "https://graph.microsoft.com/v1.0/groups/$($groupID)/drive/items/$($parentItemID)/children" `
        -Headers @{"Authorization" = "Bearer $($accessToken.AccessTokenCredential.GetNetworkCredential().password)"} `
        -Body $sendBody `
        -ContentType "application/json" `
        -Method POST

    if($null -eq $responseBody)
    {
        return $null
    }
    else
    {
        return $responseBody
    }
}