Here is what I just did and it seems to work.
In the browser click on the Plugins tab
Click on the Instruments button
Select "Manage Layouts..." from the Plugins dropdown
Rearranged the synths in the plugin manager
Click the save icon
Add description "X2 Producer Instruments"
Add file name "X2 Producer Instruments.pgl" and save
Select "X2 Producer Instruments" from Plugins dropdown in browser
The browser retains and displays the Instrument layout I select in the project.