You can use workflow with condition to “Display List” and only show “Items from #21” - means you need to keep track of which page you’re on with a custom state and also calculate which # is the last page so that the action only happens when you go to that page.
The sorting (a-z), (z-a) doesn’t appear to work on the second repeating group even though it lies within the same group where the sort is being applied in the workflow.