Last time I tried webhelp, it worked with book-sized pieces, however, rather than set-sized pieces. Looking at an issue in my list, I see that a sufficient solution would be a floating, hideable, left-menu, <set>-level table of contents.
I’m imagining separate HTML (one for single-page output, one for chunked) that gets pulled in on the client side. Who has already done this using the open source stylesheets? (Maybe starting with the olink database?)