How to create sub-task

I know this is a stupid question, but I still don’t know the answer…
Is it possibile to create sub-task (I mean i.e.:step 1: create universe. sub - task 1: create sun, sub task 2:create world and so on)
How can I do?

TIA
Renato

Pressing Tab on a task will make it a subtask of the task located above. There is also a button in the small toolbar above the task table which does the same, an a context menu item “Indent”.