Maybe I just couldn't find it, but there was a mistake in one of my filters and I couldn't find a way to update it. It seems I would need to re-create it after having selected all the correct sub-filters again.
So if that's the way things work at the moment, I think it would be great if we could add new elements to a filter and click update somehow. The UI could detect a change and show a little button to save the changes.
Yes, right now there is no update option. it is a bit complicated from a UI point of view.
This was implemented quite a while ago.