John Lowther explains Additional Field Information (How to find what goes into a column that contains static values)
Additional Field Information (How to find what goes into a column that contains static values) – Accidental Administrator – GP Non-Technical Blogs – Microsoft Dynamics Community
Microsoft & the GP EcosystemTips & Hidden Features
Archived post from 2012. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.