A scrollable sidebar with sections, the section headers stick to the top or bottom of the sidebar when scrolled out of view, and are clickable to expand.
Features:
Sticks section headers to their parent's div edges top or bottom on overflow
All heights of sections, headers, and sidebar are flexible
Clicking Section title smooth scrolls it to the top
Supports window resizing
Matching Webflow UI
Ticks collapse item, name links to it (Section 2 is collapsed on load)
Still scrollable if cursor hovers over fixed item by mousewheel capture
Supports DOM injection (Section 7 is loaded in 2 sec on load)
To-Do:
Make collapsing/showing section content smooth scroll work in combination with updating the snapped elements on bottom