As per our requirements
When we find any bug in the story then we want to create a bug from the parent story for this we added some post functions its working fine. we added a new transition create a bug in the story issue type workflow so when some one finds a bug in it, this will automatically creates a bug (bug issue type). I have added a screen to Create a bug transition button with summary, description, Priority so when someone wants to create a bug from parent story than they can enter summary, description and priority (of newly created bug) but it is updating the current parent issue instead of newly created issue.
All I want is when some one clicks on the transition "Create a bug" a pop up screen appear and users needs to enter summary, description and priority but it should reflects on newly created bug instead of parent issue(current issue).
