I learned something today. This issue came from the Dynamics GP Community Forum. A poster was using Modifier to try and make the Posting Description field in the lower scrolling window of the Analysis Posting Detail screen a required field. She did everything right. Changed the field property to Required, modified the Alternate/Modified Forms and Report information and restarted Dynamics GP. Still, the 'Required' property was not being enforced. What's up?
What was up is that Dynamics didn't check that row to make sure all required fields were completed. It doesn't have to check because none of fields are required by Dynamics GP out of the box. So, if you're trying to make a scrolling window field required and it doesn't seem to work, make sure there is at least one required field on the scrolling line.