Install gnome-shell-timer by entering the following commands in the terminal:
sudo apt update sudo apt install gnome-shell-timer
Description:
GNOME Shell extension providing a countdown timer in the top panel
Installing this package adds a timer application to the GNOME Shell top panel. With it you can start a timer of any duration and when elapsed, you'll get a notification. You can also preconfigure various durations to avoid having to retype them. . It's a natural replacement of the "timer applet" for GNOME 2 (or 3 in fallback mode). . Users of the Pomodoro method will find this extension very useful.
Homepage: https://github.com/olebowle/gnome-shell-timer
Version: 0.3.20+20171025-2
Section: universe/gnome