Sincerely,
I’d replace those buttons with the same functionality taken by Windows aero-peak: for example is possible to drag&drop a firefox tab to re-order it, move it to another window, and maybe also drag a window to a side screen to place it at 50% and so on…
What could you think if would be possible to drag&drop DevTools panel to side of Firefox window and dock it to each side or to bottom and so on? if dragged onto Windows bar, it will be undocked to a separate window.
Even better if this could be made also for each panel of DevTools (as I suggested in another thread ) to improve usability