How to auto-assign Action Plans or Checklist based on the category selected in HR Helpdesk ?

We are currently looking for a solution where system can auto-assign existing Action Plans or Checklists based on the HR Helpdesk category selected in Helpdesk request. Though agent can manually select and assign an Action Plans or Checklist. But since it is manual, it inherently prone to incorrect selection or skip selection.

We are using Next Gen Helpdesk.

I found a post where someone referred Doc ID 2607150.1, but when checked, no such document found exist.

Also, I found another document which confirms that the requirement can be achieved using Groovy script (sample below), but not sure where we have to add this Groovy script (may be Server Scripts in App Composer). I would be thankful if anyone can share information or a use case on this topic ?