how to adjust to the task with subtasks we have a structured form (in the form of a tree of tasks and not a general list)

[Nic Brough -Adaptavist-]

I'm not quite sure what you are looking to achieve here. 

I think you have a set of tasks with sub-tasks, so you want something like

• ABC-123
  • ABC-128
  • ABC-129
• ABC-124
  • ABC-125
  •  ABC-131

And so-on.  JIRA supports that with tasks and subtasks.  But I don't understand what you want.  Is it importing stuff?  Something about the display?  Etc?

[Marc Jason Mutuc]

I don't think its possible. There is only a single tier under Parent Tickets which are the Sub-Task Tickets. You will not be able to do a tree structure with that.