I’m in the process of reorganizing a document library and wanted to store all of the documents in alphabetical folders. Yes, I’m using metadata, but I’ve passed the magic 5,000 item threshold and want to rearrange the library and leverage a rich search experience.

So, using PowerShell, how do you create a bunch of folders going from A to Z?

$siteURL = "https://sharepointed.sharepoint.com/sites/parent/child"

$conn = Connect-PnPOnline -Url $siteURL -Credentials (Get-Credential) -ReturnConnection

try{
(65..(65+25)).ForEach({     
$xy = [char]$_    
Add-PnPFolder -Name $xy -Folder "/mylibrary" -Connection $conn
})
}

catch{ Write-host -f Red "Error:" $_.Exception.Message}

More information about creating folders using ASCII:
https://devblogs.microsoft.com/scripting/use-powershell-and-ascii-to-create-folders-with-letters/