While we do the heavy lifting to categorise your transactions so you don't have to, on occasion we may not be able to identify individual transactions. If transactions are missing information like a merchant name or a category, it's because we weren't able to identify the transaction.
You can select those transactions and manually re-categorise them to a new category by clicking on the transaction and then clicking on unassigned/uncategorised in the detailed transaction view. From there you can select a new category and reassign the transaction.