Your own pages in the guide, from Markdown in the repository, and a preview before they merge
A Markdown file under .ib/guides/ in the repository is now a page of the guide: a getting-started walkthrough, a launch checklist, a glossary, under Guides in the sidebar next to the pages the theme produces. Front matter names the page (title), groups it (category) and orders it (order); relative links such as ../sections/hero open the page they name; search finds its headings; kept versions keep it. A push that changes only files under .ib/ shows on the guide within seconds, without a run, as does Read notes now under Theme docs. Open /t/your-address/preview/a-branch, signed in, to read the guide with that branch's .ib/ over it before merging.
Guide pages and notes are never sent to the model that writes the guide, so adding or changing one costs nothing. A push that changes theme files too still regenerates the guide ten minutes later, as before.
The pages in a preview are those written from the published theme, so a link to a section the branch adds has nowhere to go until that section is deployed and the guide regenerated. Only members of your team can open a preview; nothing of it is kept.
More in Theme documentation.