We use the opportunity solution tree in our product teams, and so parent-child relationships are really key to visualizing ideas.
Currently I've hacked this by creating new fields and then relying on tagging. We have a field for type (opportunity/solution), and then a field for opportunity (opportunity names), and then a field for parent opportunity (parent opportunity names)....
But as you can imagine, it's not very scalable, and anytime we find a new opportunity, it's quite a bit of faff
Does Jira plan to bring this functionality to JPD in the near future?