@RAVITEJAS5476 In App Studio, there isn't an out-of-the-box section or dashboard to reassign a case from one operator's worklist to another operator's worklist without opening the case or customizing anything.
The available option is to use the Transfer Assignment action from the Actions button after opening the case. To achieve your requirement, you would need to create a custom solution.
@MarijeSchillern , Yes you are correct, there is no OOTB option available for the applications built on "Theme-Cosmos", where as we have this bulk actions feature for the applications built on "UI-Kit". As per Pega recommendations new applications are to be built on Theme-Cosmos/Constellation. So, we have to wait for latest updates from Pega on this.