I'm running Linux Mint 19 Tara. When I'm running cinnamon with connected external monitor and I close the lid, notebook goes to suspend mode. This is my expected behavior.
But running xfce, closing the lid just makes external monitor the primary monitor. Moving all xfce panels and windows from notebook's display there.
I've set up xfce power manager to put the computer to suspend.
I found, that there suppose to be some advanced settings button.
This button is not avaliable.
Xfce Power Manager 1.6.1 Version
:~# xfce4-power-manager -V Xfce Power Manager 1.6.1
Xfce Power Manager Settings Version
:~# xfce4-power-manager-settings -V This is xfce4-power-manager version 1.6.1, running on Xfce 4.12. Built with GTK+ 3.22.30, linked with GTK+ 3.22.30.
EDIT - As @xenoid correctly commented, for most people, expected behaviour is to move all windows to external monitor when the lid is closed. I do not want this behaviour, I'd like to put my computer to sleep. It works under cinnamon.