How can I use PowerShell to update a GPO for a scheduled task on workstations?

If you're trying to automate the GPO edits, I suggest embedding the whole scheduled task XML into your PowerShell script using a "here-string" with parameterized values. After a simple parameter change, it’s quick to execute without diving into the GPO editor.

You might want to consider storing the script on your netlogon share and have the scheduled task call it directly. It’ll make it easier to update the script rather than modifying the GPO each time. This way, all you need to do is change the script when necessary, rather than the GPO itself.

I think you're overcomplicating it a bit. If it's just a 5-minute yearly task, is full automation really worth it? However, if you really want to edit the GPO directly, you could directly modify the XML file in the GPO folder structure using PowerShell. Just be cautious with direct editing.

How are you currently setting the version number? You could simplify this by using a file that holds the version number, which your script reads from when it runs. This would let you update the version easily without needing to go into the GPO.

Since you're dealing with proprietary GPExtensions for the software, I understand why GPO deployment is tricky. But have you considered if the software itself could be made more GPO-friendly? It might save you a lot of headaches in the long run.