Comment 10 for bug 1386778

OK, so one way is dragging the font onto http://www.impallari.com/testing/index.php and clicking "OpenType Features" and seeing what "font-feature-settings" pop up – these are usable under Features in Inkscape (I was able to get what I wanted with features "salt", "fina", "init").

Basically Inkscape is just missing a few of the buttons that that web page has :-)

(They're also listed at https://en.wikipedia.org/wiki/List_of_typographic_features)