Maybe it's better to make a mode on icon (p2.svg) with a different color, such as red, for example (or even to place in settings input for color). When I enable proxy, I forget to disable it too often. With a colored icon, there is more chance to detect its active state.

P.S. I already made it for myself but may be it will be usefull for anybody else.
P.P.S. Not much that helps, forgot turn off again. :)