Answer
This can be a genuine framework-level gap for that specific field/view combination rather than something fixable through configuration — if a field is confirmed to exist on the view but simply doesn't show up as a Column Chooser option, that's worth raising directly with IFS Support/R&D. In the meantime, a workaround is to expose the same data as a read-only custom field instead — you can view the data that way, though you won't be able to edit it through that custom field.