TestCase Setup Scripts have a little green right pointing arrow, 'Runs this script' that you can click on that then executes that script even though you are not running the TestCase.
It would be nice if that same 'Runs this script' functionality existed for the different event scripts, such as the TestRunListener.beforeRun, or the Script Assertions or Groovy Script TestSteps.
In somes cases, such as the events, you might have some initialization stuff (like my beforeRun sets up a bunch of global properties). Runs this script allows me to both test my code works as expected in addition to running arbitrarily. Adding it to Script Assertions and Groovy Script TestSteps allows me to test the code as I'm writing it.