After a couple of misfires with my computer acting like it could not keep up with all its tasks, I rebooted and tested the small orange marbles rolling down the Triple Splitter Small Feeder to the (top of the) Triple Splitter, where they immediately fall onto the Triple Splitter Small Marble Catcher, down onto the Little Wiggly Track and finally to the Right Side Small Landing Zone.
They worked perfectly! (So long as someone (Mr McGlue stood where the lower end of The Outer Spiral will be, allowing the marbles to bounce off him and remain between the rails of the Triple Splitter.)
As of this writing, just after the Triple Splitter Small Feeder has been placed: