Install xfce4-xkb-plugin by entering the following commands in the terminal:
sudo apt update sudo apt install xfce4-xkb-plugin
xkb layout switch plugin for the Xfce4 panel
The xkb plugin shows you the current keyboard layout and allows you to switch to different defined layouts. . The plugin itself cannot be used for defining the keyboard layouts one wants to use, this is done the XKB way - either in your X config or by setxkbmap tool.