.Button--disabled copied in the browser, will find exactly 1 definition in the project. .components_submit_button__normal__abc5436 will not find you anything.
And, yes I understand that you can have grep output a path name and pass that directly in as an argument to your text editor. Similarly, it'd be relatively trivial to write a bash function that'd parse the class name and find the correct file to open.
Something like:
function lookupcss() {
find . | grep $(expr "$1" : '\(.*\)__.*' | sed 's/_/.*/g')".*\.css$";
}