22nd-March-2019: Pandoc and ePub
Pandoc seems to handle putting multiple Markdown files into an ePub file as if they were all of one document, as the table of contents of an ePub that I generated using Pandoc listed all instances of H1 headings as top level items, rather than making them sub items of a top level item that accorded to each individual file inputted. One file included multiple H1 headings, and the headings were all represented in the TOC.
I used the guide here that shows how to generate an ePub file from multiple files, and I learned that I can place the input files' names all on one line — I don't need to break the file names onto multiple lines, with a backslash to indicate that the same command is still proceeding on (or at least I think that's what the backslashes are for).
This is all in an effort to produce ePubs prior to pushing any changes of one of my books to Leanpub — letting me stay on their Free tier.