Your comments

A lot of other programs have such a feature. I see this in "evernote", "producteev" and "remember the milk".

I just use version 2.7.881. Using the filter "done" makes it possible to see the done tasks of a project. That's OK and very helpfull.

Ich benutze zurzeit die Beta-Version. Wenn ich die Änderungen kennen würde, könnte ich mir diese auch gezielt anschauen. So entdeckt man die Änderungen ja nur zufällig.
I think "Create sub projecs, and then, of course, sub-sub projects" is the same as this task.
I also like to have subtask. I need this to get some stucture into the big tasks.
I forgot: There is no proxy.
Sorry for the delay. I set the path to the dropbox folder, the email und the password and I set "import and export".
Do you need more information?