Among the many new iPad multitasking features in iOS 13, Slide Over has gained some welcome new flexibility.
First, you can quickly swipe between recent Slide Over apps. Just tap the bar at the bottom and swipe right for the previous app. Swipe left for the next.
The second useful tip here is that if you swipe up with that bar, you’ll see all recent apps fan out to the right. My list of apps goes back quite a ways (I use Slide Over a lot), but I’m not sure how iPadOS decides when to drop apps from this list.