Welcome @Reitei17,
Since you prefer mouse-based navigation over other keyboard shortcuts or even other mouse event as mentioned by @TheAlmightyCheese, @qwertz155, @Zulqarnain0020 !
we’d like to highlight a feature many Opera users overlook: Mouse Gestures.
Opera has a powerful mouse gesture system that lets you perform actions by holding the right mouse button and moving in a pattern. For closing tabs, you don’t need to click the × or even the tab itself. Instead, you can:
Go to any empty area of a webpage (not the tab bar). Hold the right mouse button and draw a quick “down, then right” gesture (⬇️➡️). Release the right button — the current tab will close instantly.