Unmanaging Bulk Nodes using Powershell

There is a sample PowerShell script for bulk unmanaging nodes here:

SW PowerShell Bulk Unmanage API script

ServiceNow has a PowerShell activity designer, which is what I believe you are looking for to achieve integration:

https://docs.servicenow.com/bundle/helsinki-servicenow-platform/page/administer/orchestration-activity-designer/concept/c_PowershellActivityDesigner.html#c_PowershellActivityDesigner

There are quite a few conversations (with answers) about how to do this. Have you searched the Thwack forums yet?

https://thwack.solarwinds.com/search.jspa?q=unmanage%20nodes%20powershell