Considerations

• Up to ten fields on your compact layout populate the record highlights section at the top of each record view in the Salesforce mobile app. The record highlights section in Lightning Experience uses the first seven fields on the compact layout. However, the number of fields that display can vary based on the width of your screen, which record page is being viewed, and the permissions of the user.
• Changes you make to a compact layout are reflected in both Lightning Experience and the Salesforce mobile app.
• Each record type can have only one compact layout assigned to it. However, the same compact layout can be associated with multiple record types.
• Compact layouts aren’t assigned to profiles or individual users. To display different sets of fields in records by use case or role, create record types for the object, then assign the appropriate custom compact layout to each record type.
• If a user doesn’t have access to one of the fields that you assign to a compact layout, the next field on the layout is used.
• A compact layout must contain at least one field.
• Don’t make the primary field a lookup field. Doing this could result in navigation issues in Lightning Experience and the Salesforce mobile app.
• Removing a field from a page layout doesn’t remove it from the object’s compact layout. The two layout types are independent.
• If you change a field on a compact layout to an unsupported type, the field is removed from the compact layout.
• Before you can delete a compact layout that’s set as the primary compact layout for the object, you must choose another compact layout to replace it.
• In the Salesforce mobile app, tasks automatically show whether a task is open or closed and the due date (depending on a user’s access to activity dates). When customizing a task compact layout, you don’t have to add these fields to the Selected Fields list.
• Compact layouts installed from a managed package are editable. However, we recommend against editing compact layouts installed from a package, as doing so can cause destructive changes to your org. Instead, clone the installed compact layout and make your changes to the clone.
• Compact layout assignments are subscriber controlled. If a user installs a managed package that contains a compact layout and then changes the compact layout’s assignment in their org, the compact layout’s assignment isn’t overridden when they later upgrade the package.
• These considerations apply to Chatter:
  • In the full Salesforce site, a compact layout determines which fields appear in the Chatter feed item that appears after a user creates a record with a quick action.
  • To avoid inadvertent sharing of information through the feed, the Task page layout determines the fields shown in the Chatter feed items for tasks created using a quick action.
  • Primary compact layouts determine which fields are shown in Chatter personal digest emails.

Limitations

• A compact layout can only contain fields from its object, including a formula field that is a cross-object reference to another object.
• Fields that aren’t available in SOAP API don’t show up on compact layouts in the Salesforce mobile app.
• Compact layouts support all field types except:
  • Text area
  • Long text area
  • Rich text area
  • Multi-select picklist

Note: The content is from the help manual but the key points are highlighted to gain attention