Guided access
Can you use guided access in split screen mode on iPad?
iPad Pro 12.9-inch, 3rd Gen, Wi-Fi, Cell
Hi pwilkesedwards,
Welcome to the Apple Community.
Apple support has an article online that outlines what you can do in guided access.
You might want to select your iOS at the top of the article, for the most accurate information
The article doesn't mention split screen mode.
It does describe how to disable areas of the screen.
https://support.apple.com/en-au/guide/ipad/ipada16d1374/ipados
Hope this is helpful to you :-)