Zenity is a very useful utility which let us create graphical user interfaces for our shell scripts. Several widgets exists, and can be used by invoking the program with the respective options. The widgets are based on the GTK toolkit, and return the result of the user interaction either on the standard output or as a return code.
This is a companion discussion topic for the original entry at https://linuxconfig.org/how-to-use-graphical-widgets-in-bash-scripts-with-zenity