Editing the XenDesktop Farm policies with PowerShell is not that hard, if you know how. I couldn’t find much, if any, documentation about the subject (only some for XenApp 6), so here’s a quick how to:
First, you start with adding the necessary Citrix PowerShell modules with (you perform this on a XD Controller on another machine with the XenDesktop SDK installed):
Add-PSSnapin Citrix.*
For convenience, we’re going to map the XDFarm policies to a drive, so we can browse it easily:
New-PSDrive XDFarm -root \ -PSProvider CitrixGroupPolicy -Controller <FQDN of a XD Controller>
From there you can browse the XD Farm policies easily:
Set-Location XDFarm:\ PS XDFarm:\> Get-ChildItem User Computer
If, for example, you would like to add multiple session printers to the Unfiltered User policy you would perform the following:
Set-ItemProperty XDFarm:\User\Unfiltered\Settings\ICA\printing\SessionPrinters
-name Values
-value @("<pathA>,model=<modelA>,location=<locationA>","<pathB>,model=<modelB>,location=<locationB>")
So, there you have it 
Do note that you’re working with an in-memory version of the CitrixGroupPolicy object. That means that if you change settings in the Citrix Desktop Studio, this won’t be reflected in the current instance. Changes that you make however will be automatically written back to the XenDesktop database.
