Convert task to subtask and vice versa

Convert a task into a subtask 

You can convert tasks into subtasks, assigning them to another main task.

1. Find the Options menu [...] in a task and select Convert to subtask.
2. In the next dialog you can search for tasks in the project to which you want to assign the task. A suggestion list shows you the recently opened tasks.
   
   

Turn a subtask into a main task

Subtasks can be converted to a main task in two ways.

Either in the subtasks section within the task details by clicking on the 3-dot menu of the subtask, select  Convert to task.

Or, if you are in the detail dialog of a subtask, click on the 3-dot menu in the upper right corner and select Convert to task.