The Groovy plugin provides a step for running user-defined Groovy scripts.
Groovy is an object-oriented programming language for the Java platform. It is a dynamic language that can be used as a scripting language.
To view available steps, in the process designer Available Plugin Steps, selectScripting > Groovy.
This plugin has the Run Groovy Script step for you to add to your processes.
For information about Groovy, see https://groovy-lang.org.