here is the use case:  
Pavel just entered a comment on a work item. When I looked at it, I realized that comment should become a new work item.  

As is functionality:  I have to go hit the Create button, and do the work to create it as a subtask, copy and paste other details for both of the features, forcing me to have two browser windows open concurrently to make sure I line everything up correctly between the parent and child ticket.

Desired to Be behavior: 

I would click a button somewhere within Jira, ideally next to the comment.  it would start a Create issue to create a new work item on the same project, with default making it a subtask of the existing task.  The comment would populate the description field.  I could then edit the new ticket as I would during the Create issue functionality and save it.

Similarly, within a story or task, it would be great to have a button to press to create a child of that item with a bunch of the things defaulted.