Dear @nealumphred,
Once again, I don’t think you understand WordPress’ plugin repository. Most of the plugins here are programmed by volunteers. Volunteers who have day jobs, many of them can’t keep up with maintaining their dozens of years old plugin.
I gave you what I’m allowed to do in this forum. I’m not allowed to help you directly outside of this forum. I’m also not allowed to fix it for you, which I would have done if it was allowed. I don’t say I like these kinds of rules, but they are in place, so we have to follow them.
Should I assume my problem cannot be fixed and simply delete the Secondary Titles plugin?
I’m sorry, but yes, please delete the plugin and find a replacement. I gave you more support during my little free time than most others, but you – for some reason – refuse to at least share WP’s Health Status. To make it easy for you, I recorded it, step by step, but you stuck because you can’t see the cursor for a few seconds. If those seconds were important, you can be assured that they would have been in the video. The video itself still shows
I’m sorry to say this because I actually like to help out people. However, you behave a little bit too entitled, and under these circumstances, I’m no longer willing to spend any more of my free time fixing your individual issue.
Please read up on plugins and WordPress; maybe that solves some of your questions. There are great resources on WP’s Codex.
All the best to you.