A few people have already mentioned some items missing in the Smart Splitter list.
There are some items that I don't think they'll ever go through a Smart Splitter, like HUB parts.
I think that all items in the game should be on that list, that way people can use it for any item they wish to sort.
The items missing from the list that I know of are:
Mercer Sphere, Somersloop, Hard Drive, Battery, Heat Sink, Silica.
(I am aware that the last 3 aren't fully implemented yet, but they are obtainable)