Install xfce4-genmon-plugin by entering the following commands in the terminal:
sudo apt update sudo apt install xfce4-genmon-plugin
Description:
Generic Monitor for the Xfce4 panel
This plugin repeatedly spawns the indicated script/program, displaying its output as a string in the panel. It is useful for periodic status monitoring.
Homepage: https://goodies.xfce.org/projects/panel-plugins/xfce4-genmon-plugin
Version: 4.0.1-1
Section: universe/x11