I was wondering about a way to hide the Sidebar while using opera, whithout going to settings and clicking enable and disable, and as far as i know there is no way to do it automatically, but i found a way, what you have to do is set a shortcut that will allow you to enable and disable using the keyboard, you just need to go to settings, advanced settings and search for Shortcuts then assing a shortcut to that accion.
Am Victor, Thanks!,