Unable to resize windows of split screen

Hello tgun1985,

Thanks for that info and for choosing the Apple Support Communities. If I understand correctly, you are unable to adjust window width when using the Split View feature on your Mac. You can figure out if unexpected behavior is related to a user file or setting by trying to reproduce the issue from another user account. This process includes creating a new user account, logging in to it, and testing for the issue.

How to test an issue in another user account on your Mac

Use two Mac apps side by side in Split View

Next, use safe mode to start up your Mac as it does the following things:

• Verifies your startup disk and attempts to repair directory issues, if needed
• Loads only required kernel extensions
• Prevents Startup Items and Login Items from opening automatically
• Disables user-installed fonts
• Deletes font caches, kernel cache, and other system cache files

Log in to your user account and test the issue while in safe mode and then restart normally and test the issue again.

Use safe mode to isolate issues with your Mac

Graphics performance limited in macOS Recovery, safe mode, or Guest User mode

Cheers!