Depends on your distro but on Debian+XFCE I use ARandR (front-end to xrandr cli tool, which is a front-end to xorg's randr). Laptop plus external monitor works

Depends on your distro but on Debian+XFCE I use ARandR (front-end to xrandr cli tool, which is a front-end to xorg's randr). Laptop plus external monitor works great, with auto-config on connect and other stuff.