Is there a keyboard shortcut to switch the cursor between panels of iPad split screen?
Control Option Left Bracket and Control Option Right Bracket should allow the user to switch between the two apps displayed
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If you […] try it twice, you should find it indeed moves you to the application on the other side of the screen.

https://www.applevis.com/forum/switching-between-apps-split-view-ipad-using-keyboard-commands