Start Menu Layout Group Policy

The File is open as long as a user is logged on and using it. You can only alter the xml-file when no user is using it.

Regarding where to put the policy setting: For best practices you should never mix computer-policies and user polices. You should use seperate user-policy objects and seperate computer-policy objects.

GPO-Design is a complicated topic though and as I can't know your adds- and gpo-design principals I really can't tell you where to put it in your environment.

It will work if you put it in the same gpo as the startmenu setting and then make sure you apply this policy to all your session hosts. The session host itself is a computer-object, and as such will only apply the computer-policies from the gpo (the loopback-processing setting). Every user that logs on to the session host will evaluate all user-policy settings that can be found in the path to the session host object in ADDS and apply them (the startmenu layout setting).

Tim Hunter