Using the "old" issue view, sub-tasks can be added to Epics using the "more(...)" button at the top-right of the screen.
There is no way to add sub-tasks to epics using the new issue view.
Jira Software cloud
- Enable the new issue view
- Create a Jira Software classic project
- Add an Epic to this project
- Click more(...) at the top-right of the screen
The option Create sub-task is visible
The option Create sub-task is not visible
Disable the new issue view by following the steps described below (not applicable for next-gen projects):
- Go to Jira home page and click on the avatar at the bottom-left of the screen and then click on Personal settings
- Under Jira labs, next to New Jira issue view for software projects, disable this feature by clicking on the green button (it will become gray and a feedback pop-up will appear)