To change a sub-task to a task you can select the menu option (...) on the top right and select the option *Convert to Issue*. This will automatically let you convert the sub-task to another issue type of your choice.
Also, if you want to convert a task to a sub-task, you need to perform the same step above and select Convert to sub-task.
However, it is important to note that, to be able to convert a task to a sub-task, the task can't have any sub-task within it, because you can't convert a task to a sub-task and let a group of sub-tasks without a parent task, does it make sense?
Please let me know if it helps.
Connect with like-minded Atlassian users at free events near you!Find an event
Connect with like-minded Atlassian users at free events near you!
Unfortunately there are no Community Events near you at the moment.Host an event
You're one step closer to meeting fellow Atlassian users at your local event. Learn more about Community Events