Which SR version are you on? Firing a custom event from a listener is already a built in feature.
Go the Script Listeners page and click "Fire an event when condition is true."
You can configure when you want to fire the event and which event to fire.
If you need to create a new custom event, you should see this page in the Atlassian docs:
My partner and I were planning this relocation for years. It was our shared dream to try and live in another country. As children of immigrants, we already have experienced this once, but this still ...
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