Originally a Mac thing.
Some versions of Linux let you customize any of it. They call them Panels and I can have one on any edge of the screen or have them float somewhere. I can center the content, align left, right or if side panels, top, middle, bottom etc.
“Any of it” is right! If one want’s to dive deep every single element of it can be customized. You can even make your own custom desktop or distro. I have been working recently on adding custom GUI to command line programs. It is actually pretty easy. Basically just simple redirects from the graphics to the command program.