Hi Bas,
I'm not sure what your model looks like. If you can provide some screenshots of the domain model and page, that would help.
If you've set the Listview with source Association, you’ll be able to retrieve the not committed objects from memory + the committed objects. If you want to indicate which objects are not committed I would recommend using an enumeration and update the enumeration (such as ‘New’ and ‘Saved’) once you commit the object to the database. If you only want to show not committed objects I would recommend using a data source microflow and filter the list accordingly.
Let me know if you need further help.