The number of fields displayed in linked record previews or extension layouts depends on the view type, as follows:
List view: the form and interface/portal extensions support up to 6 fields previewed for the form's linked record fields (depending on the Form Width) and the extension.
Gallery view: supports up to 50 fields added to the Custom preview fields section. Select custom fields must be selected in the Preview fields section.
💡 Note: By default, up to 3 fields will be displayed when using the Gallery view if Use the same fields from the expanding form is selected. This is the default option for the preview fields.
Grid view: supports displaying up to 49 fields for linked record previews and interface/portal extensions.