I want to be able to add comments on pages so, for example, I know why some decisions were made.
Thanks Reinout. Yes, at least that's something. But then, I would also like to have a documentation property for each property, so the comments can be more contextual.
While I agree that it would be nice to be able to add annotations in pages, you can still use the Documentation property.
It's rather well hidden, but in the Properties pane you can find it for each page.