In team-managed projects I want the ability to convert standard issue types into subtasks for existing issues

Problem Definition

Recently next-gen projects have enabled subtasks as an issue type available for use. While you can now create subtasks, there is no mechanism within Next-gen to convert subtasks into Stories NOR is there a way to convert existing stories / tasks into a subtask issue type.

Suggested Solution

It would help to have the option to

• Convert To Subtask
  and
• Convert subtask to Story (or other standard issue type)

Why this is important

The inability to convert such issue types makes it really tedious to recreate issues. Sometimes a subtask becomes more complex of an issue and in turn is deserving to be it's own issue outside the bounds of that parent Story.
In next gen you have to recreate the entire issue as a type of story, whereas in Classic projects, you can just use the convert option in the ... or More menu in order change this issue type without having to create the issue.

Note: Currently there is an option via a JQL search: click the 3 dots next to the issue you want to convert, then select "Convert to Issue", However, it leads to 500 error - Internal server error when you hit the Finish button:


It causes confusion for users; if the option is not available yet, users should not be able to see and use it.

Workaround:

As a workaround, you can search the issues you want to convert and use the Move option to convert a task to a sub-task and vice-versa. 

In the move issue wizard, please select the appropriate Project and Issue Type to convert to.