what theme are you using?
There’s no need to bring the shortcode.css file down into your child theme. Once in the child theme, you’re good to use its style.css file to overwrite any CSS from any file in the parent theme (or plugins, for that matter).
So if you haven’t already, create a child theme and just work inside of its style.css.
generally, additional stylesheets of a child theme could be included with an @import rule in style.css of the child theme; or could be enqueued with some code from within functions.php of the child theme; https://codex.wordpress.org/Function_Reference/wp_enqueue_style
files in sub-folders of a theme can possibly not be edited in the appearance editor.
however, it seems that the theme ‘Victoria’ is a commercial theme, with which this forum unfortunately cannot help;
please contact the theme’s developer directly for support with your question.
http://codex.wordpress.org/Forum_Welcome#Commercial_Products
Thank you both for your help.
