The Libraries folder in Windows 11 is hidden in File Explorer, but you can easily enable it.
To show the Libraries folder, open File Explorer, click on the three dots, select Options, go to the View tab, and check the Show Libraries option.
To hide the Libraries folder, open File Explorer, click on the three dots, select Options, go to the View tab, and uncheck the Show Libraries option.
To add folders to the Libraries, open File Explorer, navigate to the folder, right-click on it, select Show More options, choose Include in Library > Create New Library, and the folder will appear in the Libraries.