When a user clicks the "Maximize" on the title bar, the application will become fullscreen. This is the behaviour of most desktops, but it is actually bad if you consider about it: When you have multiple applications at the same time on a desktop, a suddenly fullscreened app dominate the current desktop and shadows other windows. Those windows used to be presented side by side, and now they are gone from user's direct control. Image a simple situation: you have a browser for doc, a terminal for commands, and an editor for coding. You maximized editor, and your terminal and browser are gone. Bring the up is very awkward. When you minimize the editor again, you have to adjust the windows again. What if -> when you maximize the editor, it embarks on a new temporal virtual desktop, and the terminal & browser stay in the original. You now have full-screened editor and can easily use the terminal & browser by some virtual desktop switch shortcut. --- Maximizing an application means the user wants to focus on one, but this doesn't mean he also wants to throw all the other windows away. EXPECTED functionality: Option to change the behaviour of "maximize" button on the title or the "maximize" in general: When you click it, the window will embark on a new (temporal) virtual desktop, and when you click it again, it will go back to the original virtual desktop. If the original is gone, it will return to an adjacent virtual desktop. This is probably not the best design. Maybe we can add a new "fullscreen" in parallel with existing "maximize". Advanced user can opt-in by dragging the new "fullscreen" to titlebar in settings.
Typo: "Bring the up is very awkward" -> "Bring them up again is very awkward"
As long as you have a visible Task manager applet, it's actually not awkward at all. You have a visible means to see what's running with clickable buttons to switch from one to another. If you don't want the window to cover other windows, you can use window tiling to tile one window the the left side of the screen, and another window to the right. It works great when you want to be working with two windows at a time without either of them being covered up by the other. However, the workflow you describe is valid, especially if you remove your panel (as GNOME does, which is why they have this behavior by default). If you want it, you can download the 3rd-party KWin script called "Maximize to new virtual desktop". You can get it in System Settings > Window Management > KWin Script > Get New Scripts...