Install gnome-shell-extension-multi-monitors by entering the following commands in the terminal:
sudo apt update sudo apt install gnome-shell-extension-multi-monitors
Description:
Better support for additional monitors in GNOME shell
A GNOME shell extension that makes the shell more friendly for multiple displays. . You can set whether the following should be present: * Plugin's own applet * Panels * Thumbnail slider * Activities button * AppMenu button
Homepage: https://github.com/spin83/multi-monitors-add-on
Version: 0.00~git20171014.1.df5d6e4-1
Section: universe/gnome