Wunderlist has become my default task management tool.
I was looking for a way to see on a single page the list of all tasks, in the all the lists.
After lot of searching, I found a way inside Mac application of Wunderlist.
If you want to see list of all tasks on Mac (might be in other OS also)
- Click Open preferences
- Click on Smart List
- Check the option next to ALL and make it Auto
- Save and then you should see list of all tasks inside the menu option All