Install vala-panel-plugins-wnck by entering the following commands in the terminal:
sudo apt update sudo apt install vala-panel-plugins-wnck
Description:
Plugins for vala-panel - X11 plugins
Vala Panel is a rewrite of SimplePanel. It is a GTK+ 3 desktop panel written in Vala and based on ideas from LXPanel. . This package contains X11 plugins for vala-panel: tasklist, system tray, and others.
Homepage: https://github.com/rilian-la-te/vala-panel
Version: 0.3.65-0ubuntu1
Section: universe/x11