There will be soon! I just added one, so you can look forward to using it in the next patch. In the meantime, you can still click the "Collapse All Groups" command in the category or group tools menus.
If you're finding all the category headings to be too cluttering, might I suggest that you switch to using the simple grouping headers instead (sometimes we call them "category families"). Instead of having ~45 different story category headings, you just get a simple list of headings like "Events, People, Groups, Places, Things". I personally find it much easier to use this option than the many category headings, although everyone has their own preferred way of doing things.
You can find it by going to the Manage tab in the ribbon, clicking Preferences, then choosing Navigation View in the left panel, then picking "By Simple Grouping" (the first option). Or more simply:
Manage > Preferences > Navigation View > By Simple Grouping
Hope this helps!
It was probably buried in the patch notes, so it's not surprising that people didn't see it. I do appreciate finally being paid the reverence and homage I deserve, however.