Does anyone know how I can take a track that has multiple home made midi objects and combine them into a single object so that I can export the entire track as a single midi file instead of 8 bars at a time?
No, this feature is intentionally missing. It works in Samplitude Music Studio.
There is a workaround. Create a non-looping MIDI-Object over your whole song. Place the red playback line at the beginning of a small midi object. Open the MIDI editor. Select every note with Ctrl-A and copy everthing with Ctrl-C. Close the MIDI editor. Open the editor on your long MIDI-Object without moving the red playback line and paste the copied MIDI notes with Ctrl-V. It is laborious but at least it works. The question is, if this takes less time than exporting everything individually and joining it in another MIDI editing application.