Can we customize status change on click of issue-workflow-transition-submit in a worflow screen?

[saranya anand]

The workflow screen has a submit button ,onSubmit calling a custom  API .
If the API gives error response want to stop the status transition.

[Nic Brough -Adaptavist-]

Yes, you could write a validator that makes your external call and throws back an error if it fails.

If you do that though, you should think about the consequences of trying to do it - what does the remote system do with failed attempts to do things?  Does it matter that the Jira issue will not record any change or that it even tried to do something?