Workflow Tasks page, is there any way to allow a user to approve/reject an item without going into the item itself? Preferably a way to do it without custom code.
Approval or rejection of items or files in lists or libraries must be done one at a time. You cannot approve or reject multiple items or files in one operation. There is no out of the box feature available for multiple approval.
There are multiple free 3rd party tools available for this. You just have to deploy the Wsp to your SharePoint environment.
Or this one. This uses the default Approve/Reject form and saves for all selected items. https://p3bulkapproval.codeplex.com/