...
In the next step there will be a console, where a administrator can enter the script.
After the editing is complete, a administrator decide the script should be:
a) activated now - click Save and Activate,
b) tested first - click Save.
...
After go to the list of possible to add functions, select from the list: Groovy Template Conditions / Validators / Post functions.
Next from the list of created scripts, select the one to be added.
Create a test version of script:
...