Is it possible to implement a full css page into google dev tools?

I have a project where I’m writing new CSS for a client’s website, but I have no actual access to their code. To get around this, I’ve been editing the CSS in browser element by element using google dev tools. The big problem with this method is that once I’ve written all this new CSS, if the browser is refreshed I lose all of it.

Question is, does google dev tools have a feature where I can upload a whole new CSS document to override what it’s displaying in browser?

I’m going to guess no, but if it was possible it would make my life a lot easier moving forward. Thank you all.

You could inject a script using JavaScript. You could have the code run automatically with a something like TamperMonkey. GreaseMonkey for FireFox is similar and will give you many more examples. You could also use the script to remove any stylesheets on the page right before you inject the reference to yours.