I find it hard to move my Opera GX window when I have the window maximized with a full bar of tabs taking up the space I would use to move it. Shrinking the window first then moving it works but its a little inconvenient to have a 2 step process.
If I could adjust the amount of space I have between the tabs and top of the window, even a 3-5 pixel width would be enough to move the window without switching tabs or dragging one out into it's own window accidentally.