Hi Jannes, 

You can add a Boolean attribute called ProductAdded to the listview entity and use that as conditional visibility on the listview item. In the add button microflow toggle this attribute to true and refresh in client, this will hide that listview item (row).  There are several options to achieve this but it depends on what you are tying to do, for example if you are adding this product as an association to an entity then you can add XPath constraints on listview to only show products that are not added or you can also add domain model access rules XPath constraints on the entity itself.

Hope this helps!