Apple - How to split a movie into many movie files, split by chapters?
I solved this by using Handbrake.
Select the movie as the source file.
Near the upper right of the Handbrake window, there's an option to select a range of chapters. Tell it to go from 1 to 1.
Name the destination file 1.mp4, so that it can be distinguished from the other files that are soon to be created.
Start the encoding.
Repeat this process for every chapter of the movie, clicking Add to Queue so that the files will be lined up to be created immediately after 1 is finished.
Sure enough, now I've got 18 movie files that together make up an entire film!
To my knowledge, no one has asked this question online before, so I figured I'd share my answer with the world. Hope it helps someone!