Theme App settings and custom theming options together?

New here. Recently installed NC 14 with MariaDb/MySQL, Apache2, and Redis on an Ubuntu server running 16.04. Pretty happy with the theming app, however, I’d like to modify the upload button’s size and color (css) in addition to possibly adding text on the button to make it a bit more conspicuous. I’d previously attempted to theme everything myself via these instructions
and have been attempting to add my desired button changes on top of the Theme App as described in link above, but to no avail. Is this even possible? Any advice for doing so?

Nevermind. I got what I needed working. Thanks, though. Really digging this product.