Section adjustment
When you hover the top or bottom edge of a section, two discreet handles appear at the top and bottom. They let you vertically resize the section or add a new section above or below.
Lengthen or shorten a section
Grab the bottom edge handle of a section and drag down to lengthen it, up to shorten it. The minimum height depends on the content: the section can't become shorter than the lowest block it contains.
The top edge handle does the equivalent by raising or lowering the top of the section. Every block inside is shifted accordingly to keep their positions relative to the section.
Collision indicators
While resizing, the blocks that touch the edge being modified are highlighted to warn you: if you keep shortening, those blocks will limit the reduction.
Add a section above or below
When the canvas isn't being dragged, the handles offer a + button to add a new section. Click it to open the template library: pick a ready-to-use template (text, image and text, three cards, call-to-action…) and the section is inserted at the indicated location.
It's the direct equivalent of Create a section shown on an empty page, but chained inside an already-built page.