The script is part of the explanation on editing the content types available in the article here:

SharePoint Online content types in Powershell: Edit.

This example gets all content types in a single list from a single site, and changes their display form names,using:

PowerShell
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$cc.DisplayFormTemplateName="DocumentLibraryForm"
 

The script requires SharePoint Online SDK installed. Before running the script, enter the information:

PowerShell
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  # Paths to SDK. Please verify location on your computer. 
Add-Type -Path "c:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\ISAPI\Microsoft.SharePoint.Client.dll"  
Add-Type -Path "c:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\ISAPI\Microsoft.SharePoint.Client.Runtime.dll"  
 
# Insert the credentials and the name of the admin site 
$Username="admin@tenant.onmicrosoft.com" 
$AdminPassword=Read-Host -Prompt "Password" -AsSecureString 
$AdminUrl="https://tenant.sharepoint.com/sites/powie1" 
$ListTitle="notf--ked"