Unanchor panel / Free floating panel / Pop-up panel
It's would be interesting to unanchor panel from its toolbar such a way that panel becomes a pop-up for the tab. Maybe some window stuff would be needed to add like sizing and cross closing button.
Yes, this would be better than the current implementation, and similar to Opera 12.18, except that the floating panel in Opera cannot be moved outside of the window.
If one has a secondary monitor, it makes it possible to move the panels completely away from the active window.
Also useful for users who do not maximise the Vivaldi window.
Since panel is thought as a floating window, it can be then anchored to the bottom of the window as others side as suggested into this.