I've been using Opera GX for the longest time and when the browser window is maximized and full of tabs, you can grab the whole window from from the very top of the page, anywhere above the tabs.
There is also an option to disable it (in the picture). So far, so good...
2580ca6b-628c-42a2-9fc5-8c84b4588132-image.png
But in Opera One (version: 114.0.5282.185) the grabbable area starts 1 pixel below the very top, so you can't just move your mouse to the very top of the screen to grab the window, you have to hit a 4 pixel wide area that doesn't start from the edge of the screen.
I think in Opera GX it is literally just 1 pixel wide, but since it starts at the very top, it's easy to grab. In Opera One that feature, as of now, is practically unusable
