There is no Batch Update feature in the Time and Expense Reviewer screen in CORE. However, it does have the Actions > Update Rates option, which updates the rates of the selected entries in one go. The rates are updated based on the latest fee schedules or project settings (see rate hierarchy below). 

1. Does the project have a fee schedule. If yes, pull rates from Fee Schedules. If no, go to 2.
2. Does the project have the 'Use rates from the Activity Items screen' rule enabled? If yes, pull rates from Activity Items. If no, go to 3.
3. Pull default employee rates from Employees >Details.

Check CORE Help Center for details.