Hello how are you?
Welcome to the Microsoft Community!
My name is Marcelo C., I am an independent consultant, I am here to help you in the best possible way :)
Tablet Mode, which allows you to use your computer as if it were a tablet, has been completely removed. To replace, Windows 11 will have new features to dock and undock the keyboard.
This feature of grouping, renaming and resizing apps has been changed also now you will only be able to determine your main apps in one place, but without the option to resize and group them as shown in the image.
I hope the information above helps.
Have a nice day and stay safe.
Marcelo de C.