This track is ostensibly going to deliver small marbles into the Triple Splitter Small Feeder. It was a candidate for delivering small marbles to the Lower Zig Zag via its Lower Zig Zag 3F, but at the point where the tracks are closest, they are headed opposite directions. The Lower Zig Zag Triple Splitter Small Feeder Separator keeps them separated.
As of this writing, this piece does not exist.
The photo from May 11, 2019 shows its approximate position, but that space is reserved for the Outer Spiral.