The app is unusable: I can't add a list

[vporton]

The button "Add list" remains inactive (gray) and I can't add any list:

[JMoerman]

You do not seem to have selected any files to store the tasks in. Can you select/create a file for the uncompleted and completed tasks (the buttons next to "Store to-do tasks in" and "Store completed tasks in")?

If that fixes it I would say that the application isn't intuitive enough.