You can create a file without a File Type Extension in Windows 11/10 by carefully following the steps laid down in this post.

To make a file hidden, or to unhide a file, right-click on it and choose Properties and General: You'll see the Hidden check box at the bottom.

If you want to make your files automatically copy to another folder on your Windows 11/10 computer, this guide will show you how to do that.

But if you prefer to keep local copies of your Office files, or if you use alternative cloud storage services such as Google Drive, you should force Office to save files to your computer.