In order to enahnce the approach of completing tasks it is needed to do this:

When I note a task as
1. Call peter for book our trip.

And brought it done, but need one ore more action steps on it to mark the task as fully completed
So I had called Peter and agreed that I have to search for more informations.
So I would like to add a task, which depends on the 1. task. So I can track all tasks and get a history of them.
Maybe a good approach is to say: right click on the task, "one more action". That command makes it possible to name a new task which depends on the 1. like this:
2. Gather more informations about the trip with Peter

This task is know shwon as a task, no more the 2. one. But when you open the task, you can see the 1. Task as strikethrough and also can open all comments, descriptions and other things which belongs to a task.

And that approach must be endless repeatable... That feature is very important and helpful.