yes, so that has been changed.
when you are in split screen mode(multi window), swipe from right screen to left to bring edge panel, then long press one of the app you want to open (switch one of splited screen) and drag it to either top or bottom of splited screen to change the app.
I like to have video player like 1/3 screen with whatever I'm doing and there is no way to open it from app edge. so I'm having to retrain my brain to always select the video player first and then the other app.
Wish they'd revert to one UI. version or just add a recent app button next to the all apps button on the edge panel so you can have the old functionality with the new functionality