I recently found where it's possible to replace fonts on a whole document (Extensions > Text > Replace Font). In this dialog box, there is no dropdown or other way to select a font other than copy / pasting a font name or manually typing the font name correctly. This tool would be considerably more useful if it were possible to select which font is being replaced and which font to replace it with.

I am unsure if extensions fall under the correct context for this area of the forum, but the version of inkscape I am running shipped with this extension which leads me to believe it's part of the inkscape utilities.