Install xfce4-cpugraph-plugin by entering the following commands in the terminal:
sudo apt update sudo apt install xfce4-cpugraph-plugin
Description:
CPU load graph plugin for the Xfce4 panel
The CPU graph plugin displays a graph of your latest system load.
Homepage: http://goodies.xfce.org/
Version: 1.0.5-1build1
Section: universe/x11