Vaidy has a great look at Why Extender Information does not get transferred? I think this is important. Extender can be a great fit in many situations but it’s important to understand the limitation to avoid creating a mess.
Why Extender Information does not get transferred?
Development & IntegrationSales, Purchasing & Inventory
Archived post from 2010. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.