Placing the collapse/expand key (button) into the attribute keyboard is not so very handy when you just want to see what is collapsed and then refold a bulleted line. Collapse/expand works fine with headings by selecting the button from the heading icon but there is no such choice (that I can find) for re-collapsed a subordinate bullet line.
Agree, the collapse/expand button is really great, but I’d also love to have it somewhere permanently. However I wouldn’t know how that can be implemented visually clean.