some solution so that narrow windows doesn't result in categories being hidden

Would be nice if we could have one of these solutions or something similar:

**Option 1**: Have the headings fix to top and bottom of screen when not in viewport, so it's clear that there are other categories down (or up).

**Option 2**: Have something floating (say on the top right) indicating that there are other categories up or down, and lets you click to jump to them. If all the category headings are in the viewport, don't show this.