You can select multiple time entries and perform actions on them. In any time log report, Click on the next to the checkbox in the report table header as shown below:
To perform an action, you will need the appropriate privilege. Also, time entry has to be in the correct state as per the workflow. So if you try to invoice an unapproved entry the action will fail.
You can set individual attributes of time entries or update the bill and cost rates to the latest values. The latter is especially useful when you have modified the rates and you need to update time entries with the new ones.