Hi Benny,

That sounds like a very useful filter! The way I would go about doing this is by filtering the finish date column to the latest dates you care to look at and then look at the percent complete column and see what that column says for each task. Then I would create a custom column that's called "overdue tasks" and mark the tasks you see are overdue by using the finish date and the percent complete with the  word "overdue" so you can use your new overdue tasks column to automatically see what's not finished that's supposed to be in your project. Unfortunately there is no way to filter overdue tasks from the task filter button in this version of gantter. 

Let me know if this helps or if you need me to provide more in depth steps to achieving the result I described below. 

Kind Regards, Sophia