Thanks for the input.
After posting my original question above, I continued searching and it appears what I’m looking for is generally referred to as ‘chapters’, and there’s a fair demand for ‘chapter markers’ thanks to the popularity of podcasts. Apparently, there’s also support in the MP3 file format for such things, though no one has actually implemented a solution.
I found this old Audacity forum post from 2016 that describes exactly what I’m looking for - https://forum.audacityteam.org/t/how-to-create-chapters-in-a-single-audio-file/42353/1 and in it, there’s a reference to ‘chapter and verse’, and also to ‘auphonic’. There’s a suggestion that AAC supports chapter markers natively. I will read further down those paths and report back if I find anything useful.
I guess I could just split all my files into individual ‘one file per track (chapter)’ chunks and experiment with playback. Since my current music files represent ‘live’ recordings, I’ve avoided this due to un-natural gaps being heard at the transition points from file to file, but I know some playback tools offer ‘gapless’ playback. I’ve also never understood the sequencing logic of my car audio playback system; it doesn’t offer any control over playback ‘sequence’, and as far as I can tell, it does not play back in ‘file name’ sequence, so even if I carefully name all the files in alphanumeric sequence there’s no guarantee it will play them back in that order. But I will experiment further and maybe I’ll figure out their logic.