Here’s the replacement UI for the old Custom Styles screen. This is still classed as a WIP purely because I’m awaiting feedback from my colleagues as to what else they would like to be able to see appear in the list box.
You can remove Custom Styles as before but the additional feature is that you can also toggle the styles ‘Automatically Update’ status. Select the style(s) and click the button. Much easier than having to wade through Word 2013’s Style Gallery, find you custom style, then right-click on each of them to see if you want it and/or want to have Automatically Update switched on 🙂