Deep filter
If you filter a list of elements, only matching elements are shown.
However, sometimes elements can have nested contents:
You can see, that the expanded element contains other elements as its children.
In such a case, you might want, that the filter also gets applied to those elements.
Exactly this happens, after you enable the "Deep filter" option.
Lets say, you append "123" to your search above.
In this case, you would only show nested objects, that match this filter:
You can see that only a subset of the elements is shown.