I would like to make following hierarchy:
Task
-subtask
-user story
-user story
-subtask
-user story
-user story
But when I am trying to add user story as a subtask to existing task it is not possible
I would like to make following hierarchy:
Task
-subtask
-user story
-user story
-subtask
-user story
-user story
But when I am trying to add user story as a subtask to existing task it is not possible
No, it's not possible the way you want.
I suggest the most common approach and that's to use Epic -> Task/Story -> Sub-Task hierarchy.
The Sub-Task is the smallest task in Jira and it doesn't make sense to have any further sub-issues. Moreover, (User) Story is bigger piece of delivery than a Sub-Task. Common Tasks and Stories are usually equivalent issues (at the same level) and just used for different type of task.
See also these links at Atlassian Agile Coach: