Discussed during the UX working group call on 4/3/17.
Remove the current scrolling scrolling behavior / animation for the tools within the left tool menu. This semi-fixed behavior interferes with the sense of place established by the fixed header / collapse button in the new UI. Additionally, if you have a small viewport or a large number of tools, this scrolling behavior actively prevents you from accessing the site tools that exist outside of the visible frame.
The desired behavior is for this left tool menu to be static, and for its contents to scroll relative to everything else on the page, so that only the header and collapse button display as fixed in place on scroll.