Produce error when promote target doesn't exist

Hi, I’m wondering if there’s a simple non-obvious way how to produce an error if a user tries to promote to a target env that doesn’t exist.

At the moment, I have a trigger for the actual deployment step that only runs if the target is one of a pre-defined list, e.g. stage, prod, dev.

Is there an easy way to create an error if someone tries to deploy to a non-existing env like “staging” or “stg”?

Or is this something I need to create a custom check for?