The Field Helper tool examines field-related configurations, including the following:

• Field context: This checks whether the field is a custom field. The tool will then check whether the field has a context that matches the current project and issue type combinations.
• Field configuration: This verifies that the field is set to Hidden.
• Screens: This verifies whether the field is placed on the current screen based on the screen scheme and issue type screen scheme.
• Field data: This verifies whether the current issue has a value for the field, as custom fields without a value will often not be displayed.

Let's look at the following screenshot:

Total Comments is a custom field, and the reason it isn't displayed is that it has not been added to the screen.