I have created a new project. Q: How to make an existing task a sub task to a newly created task?

[Scott Stephenson]

I have created my first jira project. 

Q: How to make an existing task a sub task to a newly created task?

Thanks Scott

[Mesut Yilmazyildirim · Accepted solution]

You can convert multiple tasks into subtasks via bulk issues

For doing so, perform a search > bulk change > Move Issues.
Move into the same issue and change the issue type to sub-task.

It will also ask you the parent issue that it will be linked.

Hope it helps.

[Scott Stephenson]

Thanks