The course index now shows the whole course and marks where you are

The collapsible index on the left of a course page used to list only the current page's own sub-nodes. Standing in lesson 2 you saw lesson 2's children and nothing else — you could not tell how long the course was, what was coming, or that you were nearly done, so you navigated by the Next button and by guesswork.

It now lists the whole course: every module as a collapsible group, every lesson inside it, ordered the way the course declares. The page you are reading is marked rather than the list pruned to it — with a ▸ glyph as well as an accent colour, so the marker still reads if you cannot distinguish the colour, and as plain text rather than a link, because a link to the page you are already on is a dead control.

Nothing else changes: a doc or a space still gets its own children, and the index only widens on pages that actually sit inside a course.