Trigger is a script that is launched when some event is happening. To create a new Trigger, open Scripts panel, click  icon from the Toolbar and choose Add trigger option.

The code panel will be changed. Then, you need to:

1. Define the Name for the Trigger
2. Choose whether it is active now or not
3. Set the Event when the Trigger is going to be executed
4. Add Script — lines of code.

Before you start, visit the script documentation site to learn more about Memento Database syntax and the features of Triggers.