Binary package “kdocker” in ubuntu bionic

lets you dock any application into the system tray

 KDocker will help you dock any application into the system tray.
 This means you can dock openoffice, xmms, firefox, thunderbird, anything!
 Just point and click. Works for all NET WM compliant window managers - that
 includes KDE, GNOME, Xfce, Fluxbox and many more.