Not well integrated

I cannot even say for sure that this plugin works. The UI requires entering the subtitle in the right side panel and not inline with the post text where I’d expect it. I took 10-15 minutes just to discover this. Then I tried to preview the post to see if the subtitle rendered and it did not. So the only way to know if this plugin is working is to publish a post. I refuse to publish a post to verify the plugin works. The plugin should display the subtitle in the preview and ideally in the post editor.

I’m using WordPress 5.3.2 (which is the latest verified working version with this plugin at the time of this writing).

Reading over the description of the plugin, it appears that I must edit the theme. I’m not going to do that either. There must be a better way to add subtitles.