Getting on in years, I keep forgetting how I've done certain things. It would be nice to have a little notebook associated with each page to let me record thought jogs.

You can have that now... somewhat.

Option 1:
Open a text object on each page and jot your notes. Set the Special FX->Loading settings to hide before and after loading. While the text object will be published, it will only be visible if someone does a View Source.

Options 2:
Use a separate page with multiple text objects, one for each page in your project. Use the Page->Page Order dialog to keep this page at either the beginning or end of your project. Then when you publish, use the Page Range option to only publish the actual project pages, omitting your "notes" page.

Thanks for the suggestions. Great examples of "thinking outside of the box".