The Microsoft Dynamics GP 2013 R2 Feature of the Day: Assign an Item to Multiple Sites doesn’t seem like a big deal until you realize it’s not there in previous versions. Then it quickly becomes a pain. This is a nice GP 2013 addition.
Microsoft Dynamics GP 2013 R2 Feature of the Day: Assign an Item to Multiple Sites – Inside Microsoft Dynamics GP
Tips & Hidden FeaturesSales, Purchasing & InventoryGP 2013
Archived post from 2014. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.