Many files don't show up in the Editor in MadHat theme

InkHive Q&ACategory: Theme SupportMany files don't show up in the Editor in MadHat theme
MC Thompson asked 11 months ago

I am trying to customize MadHat for my client’s blog, however, I cannot seem to change many elements, including:
a) adding a black border on the bottom edge of the top menu. The only CSS sheet that I can edit via the Dashboard’s Editor is styles.css. I noticed that there are about a dozen other CSS sheets associated with the theme, but they do not appear as an option to edit in the Editor. The Custom CSS tool does not work. The Simple Custom CSS plug-in does not work.
b) remove the bottom menu, which we are not permitted to style, and therefore does not work with the rest of the page. I don’t know where to even begin to search for this code.