This appears to be fixed in XCode 12 beta 5 They restored an option for Style: "Unspecified (Discouraged)" in storyboard for UISplitViewController which reverts things back to the previous behavior. You'll need to rebuild the storyboard with the new version for this to take effect (simply rebuilding the project but never opening the storyboard will not work).

I was able to force this on the simulator by modifying the .GlobalPreferences.plist file If you navigate to your simulator directory ~/Library/Developer/CoreSimulator/Devices/<SIMULATORID>/data/Library/Preferences/ There is a hidden file named .GlobalPreferences.plist Make a backup of this file and convert it to XML $ cd ~/Library/Developer/CoreSimulator/Devices/<SIMULATORID>/data/Library/Preferences/ $ cp ./.GlobalPreferences.plist ./.GlobalPreferences.plist.orig $ plutil -convert xml1 ./.GlobalPreferences.plist The file should look something like this <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"> <plist version="1.0"> <dict> <key>AppleLanguages</key> <array> <string>en</string> </array> <key>AppleLocale</key> <string>en_US</string> </dict> </plist> Add the following inside the <dict></dict> section <key>SBChamoisWindowingEnabled</key> <true/> Then convert back to binary $ plutil -convert binary1 ./.GlobalPreferences.plist Now start your simulator and Stage Manager should be enabled Worked for me on Beta 3 iPad 11 3rd gen sim Credit goes to https://twitter.com/KhaosT/status/1533928828753481729 https://itnext.io/you-dont-need-gui-or-how-to-control-ios-simulator-from-command-line-bf5cfa60aed2

https://developer.apple.com/forums/thread/708567?answerId=720569022#720569022 Posted an option here