Create your own theme based on nodebb-theme-persona by making a copy of it. Give it a suitable name. Remove the classes visible-xs-inline from /templates/partials/menu.tpl in your theme folder. That does the job
@dcook The color you want to change is not property of the categories, but rather the property of the theme. Black is the theme color for section categories (non-clickable link) and blue is the theme color for non-section/normal categories (clickable link).
That's why there is no option to customize it on categories management.
Threw something quick together based on nodebb-plugin-spoilers, I also looked into extending the existing markdown plugin using the extension support the parser has, but didn't really succeed. Would be great if we could just add markdown-it extensions in the admin panel to extend the syntax, cuz there are plenty existing ones
