Thank you for your post!
The Omit Record will have to do with your found-set. You will most likely want to do a Perform Find when the database is opened as well. If you do a PerformFind when Tasks::Status where the criteria is just an equal sign (=), you will have a foundset of records where the Status Field is empty, therefore excluding the "Completed" tasks. You might see Perform Find and Refining find requests in FileMaker Pro using find operators.
You might trigger that script on First Window Open: Understanding and using Script Triggers
I hope this helps!
In a hosted database, found sets are not retained when you close the file. I would expect, however, to see it retained in a file opened directly with FileMaker rather than hosted from another computer. So if your system is a stand alone, single user file and this is happening, something else in your system is changing the found set. Since this is pretty easy to do, as TSPigeon has recommended, you may need to employ a script that produces the found set you want. In addition to OnFirstWindowOpen, you might instead use OnLayoutEnter--which is better depends on the overall design of your system and there are other options that might be used as well.
this is hosted solution that is accessed by multiple users. So, if I understand correctly, what I was trying to achieve is not possible?
It is not possible, FileMaker Server is not designed to store info needed to reproduce each user's found set for every table occurrence in every window--which is what it would have to do in order for this to happen.
Also to be considered: in a multi-user environment what you wish might be different from what another user wants. But a script running on database open will do the same things (generally speaking) independently of the user, so before imposing to others a specific behaviour of the database make sure it's accepted.