In the system, there are multiple ways to approve the shifts. The Bulk Update Status option under Time Tracking> Views is the quickest way to approve multiple shifts in one go.
Go to the Scheduling >> Time Tracking > Views
On the next page select the Date range and other details in the filter as per your requirement.
Select/check the shifts you want to Approve.
Click on the 3 dots in the right corner.
Select Bulk Status Update option.
In the pop-up window select, "Approved" from the drop-down and click on Save.