Xfce power management has a Presentation Mode to disable screensaver or suspend settings
Left click Power Manager plugin in system tray to turn it on
or use this command to toggle Presentation Mode on/off
xfconf-query -c xfce4-power-manager -p /xfce4-power-manager/presentation-mode -T
Right click and selecting Power Manager Preferences has an option to show an additional indicator when Presentation Mode is on
