When you try to display a field that is hidden in the System Field configuration using Window Customization (Window>Tab>Field IsDisplayed='N') by setting the IsDisplayed to 'Yes' in the Field customization tab, the field is not shown at all. Fields that are not displayed in the system configuration are ignored by Window Customization.

Steps to reproduce

1. Login as GardenAdmin

2. Open the Window Customization window

3. Create a new record for the Sales Order Window

4. Navigate to Tab Customization

5. Create a new Record for Tab = Sales Order

6. Create a new Field Customization record with Field = "Approved" Displayed = 'Yes'

7. Run Cache Reset

Expected result
The Approved field should be shown in the Sales Order window

Actual Result
The field is not shown in the Sales Order window