That's not the maximize button, hover over it and you'll see an "enter full screen" text pop up with two other options (fullscreen with another application, one on the left and the other on the right). It hasn't been the maximize button for something like a decade now. Double clicking the title bar is not making VS Code fullscreen or moving it to a new virtual desktop on my computer, it just maximizes the window (or restores it once maximized). I have zero desire to use Edge so I'll let someone else work with you on that.