On error log listing page, if there are multiple errors for same broken link, you can easily group them. By grouping errors, you can get the list of unique 404 links instead of finding out unique logs one by one.
As shown in the below screenshot, you will have a dropdown at the top of error logs listing table. You can select a column and click Apply. Currently, you can group error logs by 404 Path, IP Address, User Agent or Referral Link.
After grouping, if there are multiple errors with the same value of grouped column, you will see the count of the errors, next to the grouped column of the log.