Not everyone uses HTML export so they are there for the user to add to a document as/when needed.
You only need to do this once per TBX document
Actually, if you add an HTML template to a document for the first time, it becomes the default template for all HTML documents. You can always add other templates and change assignments. Using the Export Inspector is just one of many ways to set a notes export template.
This will work, though by default this exports all notes (except things like the Prototypes container) unless you disable export of individual notes. If you only want to export one note (or one page compiled from several notes, File > Export Selected Note should do fine.
People use HTML export in very varied ways so a default to ‘just’ export note(s) would likely be ideal for not one.
So in summary, the only real necessary precursor action to using export to HTML, is to add an export template (or create one of your own).
What is your end game? To have an exported HTML file, or are you just trying to get your content out?
If it is to just get content out, you can turn on the Text Pane Selector and view your memo in Preview (you’ll need to have the HTML template installed). In preview to a ⌘A to select all to put you memo on the clipboard. You can then copy and paste to email, word, etc.
Ah, wonderful!!! I can see how this would work for the whole doc., but it does not seem to export the children of the selection note, like it does for Export HTML. Most of the time I would only want to export sections, not the entire doc an not just one note.