Unable to create Sub-task in next-gen project

Summary

This YouTube video demonstrates features in next-gen project, which also shows creation of sub-tasks in next-gen project (2:20). However the feature to add sub-tasks is not available in the instance.

Step to reproduce

1. Create a new Scrum/Kanban next-gen project
2. Add an issue to the board in this project
3. Click on the issue to be viewed in new issue view (popup screen)

Expected result

Ability to add sub-tasks in the issue. Please see the screenshot below which is taken from the video:

Actual result

• There's no feature to create sub-task.
• Sub-task is not available in Project settings > Issue types page, and can't be added.