I have used left-right arrow SO LONG to cycle between parallel books, I am very sad to see that has been removed. It will be a difficult habit to break.
The new method requires a mouse click PLUS scrolling to where your current resource is in the list, then clicking on the next one. Rinse and repeat repeat repeat.
If the purpose of this UI/UIX "update" was to make things SIMPLER ... I apologize for the complaint but this is demonstrably HARDER.
Please somehow RESTORE A SIMPLE KEYCLICK as before. Alt+ or Ctl+ is fine but please don't require the mouse and scrolling!